How long would the US military last in a war against the rest of the world?

What would happen if the US found itself facing off against the rest of the world?
Not just its traditional rivals, but what if it had to fight off its allies like the UK, France, and South Korea as well?
In short, America would stomp them.
Especially if it pulled back to the continental US and made its stand there.
First, the US has the world’s largest Navy, by a lot. With ships displacing 3,415,893 tons, the mass of the US Navy is larger than the next eight largest navies combined.
And the American ships, as a whole, are more technologically advanced than those of other countries. For instance, America fields nuclear-powered aircraft carriers, and it has 10 with an 11th on the way.
And that’s before the US Coast Guard gets into the mix. While the Coast Guard isn’t an expeditionary force, it could use its C-130s and other sensor platforms to give the Navy more eyes across the battle space. Its counterterrorism operators could protect government leaders and secure American ports.
So attacking America across the water is a horrible idea. (Got that, North Korea and China?)
Second, America’s air power is the strongest in the world. Currently, it has about 14,000 planes and helicopters spread across the five services. That’s more aircraft than the next seven countries combined.
US Navy Photo
The world’s only operational fifth-generation fighter, the F-22, would conduct constant air patrols across the land borders of the US to prevent any incursion by enemy bombers. The Army’s Patriot missile launchers would help stop enemy jets or missiles and Stinger/Avenger missile crews would shoot down any low-flying planes or helicopters.
So the rest of the world’s militaries have to fight their way across a land border with the US while their air support is falling in flames around them.
Blair BuntingThe F-22 Raptor.
Guess what happens next?
The Army and Marine Corps’ almost 9,000 tanks would team up with thousands of Stryker Anti-Tank Guided Missile vehicles, Apache and Cobra helicopters, and antitank missile teams carrying Javelins and TOW missiles to annihilate enemy armor.

US Army Pfc. Victor AyalaA US Army Stryker combat vehicle firing a TOW missile.

The world’s most advanced tanks, like the Leopard or the Merkava, would be tough nuts to crack. Artillery, aircraft, and antitank infantry would have to work together to bring these down. But most tanks worldwide are older US and Soviet tanks like the Patton or the T-72 that would fall quickly to missile teams or Abrams firing from behind cover.
The other combat troops trying to make their way through the shattered remains of their air support and the burning hulks that were once their tanks would find themselves facing the most technologically advanced troops in the world.
Lance Cpl. Julio McGraw/USMCAn M1 Abrams tank fires its main cannon.
American soldiers are getting weapon sights that let them pick out enemies obscured by dust and smoke. Their armor and other protective gear are top notch and getting better.
Chances are, even infantry from France, Britain, or Russia would have trouble pushing through the lines in these conditions. But even if they did, the Marines and 101st Airborne Division would be able to swoop in on helicopters and Ospreys while the 82nd Airborne Division could drop thousands of reinforcements from planes to close any openings.

US Marine Corps PhotoUS Marine Heavy Helicopter Squadron 464 assists Marines of the 2nd Reconnaissance Battalion conduct special-purpose insertion and extraction training aboard Marine Corps Base Camp Lejeune, North Carolina, on March 13.

And all of this is before America becomes desperate enough to launch any nuclear weapons. If the enemy actually did make it through, they’d face nuclear strikes every time they massed outside of a city. And their forces still trying to reach the border would be easy pickings.
Minuteman III missiles are designed to strike targets far from American shores, but they could annihilate an advancing army moving from Houston to Dallas just as easily.
REUTERS/Kyla Gifford/U.S. Air Force Photo/Handout via ReutersAn unarmed Minuteman III intercontinental ballistic missile launches during an operational test from Vandenberg Air Force Base in California on February 25.
Navy Trident missiles could be fired from submarines in the Gulf of Mexico to destroy units waiting for their turn to attack at the border. Northern Mexico and southern Canada would become irradiated zones.
So don’t worry, America. You are already behind one hell of an impenetrable wall.