Is the U.S. immune to invasion?
Sam Hopper, works at The High School Experience
A continental invasion of the US would be nearly impossible. You have a nation with perfect natural borders in the form of entire oceans on either side. Then you have to defeat the biggest and most technologically advance navy and air force in the world (by a mile) just to get to the shores. And thats only if the US's force immense global force projection capability doesnt destroy the invading nation before it occurs. Then if by a mere miracle they beat the military and get to the US coast, they have to deal with 100 million privately owned firearms carried by an enormous civilian insurgency, many of which have been day-dreaming about such a scenario forever.
The US is big. Attacking a country that large is a logistics nightmare - it's similar to going through Siberia to conquer Russia. You're going to get spread thin, and then you're going to starve and get routed.
The US has a massive amount of force in places that could be invaded. Notice how most of the bases are in coastal areas? (Georgia, North Carolina, Virginia, California, etc) They're there for a reason - an attack is not going to come from Kansas. So, not only do they have a lot of firepower, it's already in the best spot for an invasion.
The United States has one of the most massive armed forces, so therefore a type of standard military attack would be ineffective. The only possible way the cripple the United States would be unorthodox.
Unorthodox methods such as super contagions, nuclear weapons, aliens, cyber attacks, the Illuminati, or Mine craft..
"America will never be destroyed from the outside. If we falter and lose our freedoms, it will be because we destroyed ourselves." -Abraham Lincoln
James Ware, Strong interest in History
No, the United States at its current state is not impossible to invade, but it is rather difficult. Anyone could invade the US at the moment. Just sail on by in the name of friendship then put boots on the ground and declare war. They would be admittedly wiped off the face of the Earth, but it was an invasion. Almost as successful as Napoleon’s in Russia.
The US has the advantage of being in the New World. We have the largest oceans to the West and East making an amphibious invasion a lot harder than most places. Sure there are islands one could use, but a significant movement of ships and men would be visible and will give us time to prepare. Also compared to the Old World, we do not have long lasting hostilities with our neighbors. Sure things weren’t like they were a few centuries ago (War of 1812, Mexican-American War), but currently, the US, Canada, and Mexico have been on good terms for quite some time.
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Chris Briere, Born and Raised
The US is definitely invadable, at least for a nation with nukes.
Step 1: Detonate one or two high yield nuclear war heads high in the atmosphere above the United States. The resulting EMP will knockout a large amount of Military equipment destroying nearly all civilian electronics.
Step 2: While the US is trying to stop the nation from descending into anarchy as the entirety of the economy (nearly every car, refrigerator, etc.) grinds to a halt, send several thousand well trained Guerrilla fighters across the Canadian and Mexican Boarders armed with large amounts of C-4 and other explosives. Have these operate in independent terrorist cells with each group targeted to take down a series of strategic pieces of infrastructure, i.e. bridges. This will ripe the Interstate Highway System to Shreds.
Step 3: Wait a couple months for most of the population to die to pillaging and starvation, then mark in with what ever army you want. At this point the American people will likely welcome you for bringing stability to a war torn nation.
P.S. You'll have to keep the rest of the US allies busy in order for this to really work. If you have more nukes then detonating a couple above their nations will probably do the trick.
Only Canada and Mexico share a land border with the US, and both their militaries are negligible. Even if all the militaries of the Western Hemisphere (the only countries that can theoretically reach the US borders overland without having to put to sea) combined, their combined might would be too negligible.
Everybody else would have to come by sea, and it's hard to come by sea when the US Navy on its own is stronger than all the navies of the rest of the world put together.
So for all practical purposes, at present (2016) the US is uninvadable.
Angelo Luna, studied at Santa Rosa Junior College
if you don’t care about civilian lives and soldiers lives, probably. the problem with invading the US is that there are many trained small militia groups that have AR-15’s in the US or some other legal weapons depending the state you plan to inveade. if a country succeeds in taking large parts of a state, the militia will be ready if the army isn’t coming. most of the citizens in the US are sometimes armed with pistols or semiautomatic rifles, with bullets that probably can pierce armor. the police stations across the US has some form of military grade items like weapons and armor that the police can probably give out to the militias that are fighting the enemy. the US militia obviously is small, so they’ll do guerrilla tactics to slow down the enemies advance or halt them to give the army enough time to send the soldiers to fight them.
if a country plans on invading the US, they should attack any democratic liberal state, like california or NYC since those states have very strict gun control where you probably can’t buy an ar-15 and where most of the citizens will have a hard time getting them. also, they’re the land of the anti gun where few people have guns, so guerrilla warfare will be minimal, making the enemy have an easy time invading.
Rather than write about US military defenses, I’ll take this question as if the USA had a $0 military budget. In such a case, Hawaii becomes vulnerable. Alaska might fall to a summer invasion too but would be very hard to keep an occupation force in against winter insurgency. Outlying non-state territories like Puerto Rico could fall as well.
The contiguous 48 states, however, are essentially immune to invasion as long as they don’t horribly antagonize Canada or Mexico — even if the USA drops out of NATO and alienates all other allies. Consider that the world’s most powerful military has been unable to fully subdue Afghanistan and Iraq with decades of effort — then consider the relative size and population of the USA and how much bigger a challenge that becomes.
Then consider the need for a land route (even poverty-stricken Iraq and Afghanistan required land routes, landing all your troops by boat is impracticable for invading a very large nation — that was the worry about invading relatively small Japan in WWII as well). This means you have to invade either Canada (the world’s second largest country) or Mexico (a county of 127,000,000 people) just to reach the USA. Canada has no land route into it, so you’re probably trying to invade Mexico with the cooperation of Guatemala… across a relatively tiny border from which you’ll have to fight more than a thousand miles through dense populations. You’ll be very lucky if you still have any sort of army by the time you reach the USA border — realistically the only country Mexico is geographically vulnerable to is the USA.
There is one and only one plausible way to invade the USA (nuking it into oblivion doesn’t count as invasion, that’s obliteration): make the population of the USA believe you’ll provide them a better go nment than what they’ve got. If you’re welcomed as liberators by most of the populace, then you have the allies you need to take on small insurgencies.
Outside of Hawaii and possibly Alaska, the USA is ironically probably the nation with the least need for defense spending in the whole world. And yet the nation that spends so much more than any other and in the process makes itself less safe, putting its soldiers in vulnerable places and meddling with other go nments to create instability that breeds international terrorism.
Steven Helferich, Born and raised in the USA
From a conventional military standpoint? For all intents and purposes, yes. To successfully invade the United States, you'd need a blue water navy capable of defeating outright the US navy while also carrying an invasion force to North America.
I know some people might argue that this is not a requirement, but you need to think beyond just getting the troops to American soil. You will also need to maintain supply lines throughout the invasion. This is hard enough even when you're not trying to ship men and supplies 3,000 miles across an ocean full of hostile enemy vessels. Even at the end of WWII, when the US had undisputed control of the Pacific, it still balked at going for an all-out invasion of a much smaller and weaker opponent due to many of these issues. It took 4 years of constant warfare just to gain control of vital island territory to support military activity. I think it's simply impossible to maintain a fighting force in North America without directly defeating the US navy and taking naval superiority. This is obviously a daunting task that no single nation is capable of achieving currently. Even combining all the world's major navies may still not be enough, especially considering you'd have to organize a dozen different countries, some who hate each other, and many of which have no modern experience in conducting warfare.
There are simply too many physical and geographical advantages to the US position as well. The US has a desert to the south, mountains throughout, and a cold biome along its northern border. Invading from either Mexico or Canada would also require one of those two to break their alliances with the US, which is also unlikely. Invading the US directly along its coastline is the most geographically viable, but as I said, it brings up the issue of beating the US navy and establishing supply lines.
I've read some of the other answers on here bringing up unconventional means like EMP's. I can think of a few others like biological warfare, but the issue is that none of these deals with the US navy that is sailing around the oceans. Even if you deal damage to the general population, invasion still relies on you being able to put boots on the ground and keep them there. You can't do that while the US military is active.
I suppose if literally the entire world united against the United States, then it would be possible to invade the US simply because it would be overwhelmed. However, I'm not sure this is really the kind of answer you are looking for. I put this one up there with "Meteor strikes the Pentagon" and "entire US population suddenly falls into mysterious coma". Another might be bribing enough US admirals that you gain de facto control of the US navy in the case of a conflict. This way, you gain control of the seas from the get-go. Invasion would be much easier in this case, although occupation would still be a problem. These are all possible scenarios, but they are so unlikely that it's not useful to take them seriously.
Maybe in 50 years if the US declines and states like China and India develop navies that can go toe-to-toe with the US, I might change my answer. Until then, it'd require such an unlikely combination of factors that I just don't think you could seriously attempt it outside of a sci-fi novel.
Kevin Stern, B.S. Computer Information Systems (1997)
Nope. It’s very hard to do. Assuming our military is somehow unable to stop them from reaching our shores, resistance would be fast because our military still kicks butt. And they’ll have the people’s help (for once, so many armed citizens will be a good thing), So the invaders would be quickly kicked out. Damage would be minimal.
It’s why most US is invaded stories have our enemies using EMPs to knock out our technology, or super viruses (which mostly don’t exist) to kill us. Even then, with a virus, the goal is to kill us, not invade. That only leaves technology attack. And we don’t actually need it. Our guns work without technology. and sticks and stone do indeed break bones. In short, even with crippled technology, we’d still put up quite the fight. nay invader would be hard pressed to conquer us. Also, they might not have any tech to sue themselves (depending how long lasting a EMP blast lasts). if they do, rest assured, sooner or later we’d commandeer their tech, and sue their own vehicles, computers, etc against them. Yes it’d take longer, but we’d win. All those dystopias about no tech, and we turn one each other, ends pretty quickly when we see a common enemy.
This is why nobody’s ever tried it. It’s a losing scenario for any invader. Either we stop them from arriving, or we quickly kick them out. Anything big like disabling us, gets the rest of the world antsy. So they’ll protect themselves from a future attack. Fighting on two fronts is never easy.
Dan Holliday, lived in The United States of America
Unless you have one of these:
It's essentially un-invadable. There just isn't a collection of nations that can overcome the really vast oceans, the US Navy, Marine Corps, Army, and Air Force and, well, not to be forgotten, several thousand nuclear warheads.
Let's say all of humanity outside North America decided to invade. In WWII, two seafaring (the *most* seafaring) nations effected an amphibian invasion just several dozen miles away from southern England. It took thousands of boats. To undertake a similar invasion, they'd either have to cross into Alaska and fight their way down from there. The land between Alaska and Canada/USA proper is horrific. Then they'd be getting nuked, bombed and shelled all along the way. Up from South America? Go ahead. Cross the mountains and jungles. The land connecting North and South America is also horrific. Then there'd be the aforementioned shelling, bombing, nuking along the way.
It's not that the US isn't invadable. It is. It's just this: Would it be worth it? Would it be worth killing the millions of people in the US while losing hundreds of millions of young people? Would the sacrifice of youth from India, Russia, China, Europe be worth it? The answer is no. It wouldn't. The world saw the ugliest war in history. It took a long hard look at itself. There hasn't been a global war or a fully, mechanized war between industrialized nations since then.