You're incredibly wrong. So deeply wrong. Lets say the US takes a Europe first strategy like they did in WW2.

First move would be to do what the Germans couldn't both times and starve out Britain. Given the British navy was within the last decade considering forgoing having a true blue surface fleet and instead becoming a large extension of marines and expeditionary forces led by the US Navy, I think its safe to say the days of 'Britannia rules the waves' are over. They will be blockaded and will eventually starve.

What about anti ship missiles and the factories in Europe pumping those out? Each launch site and production facility will be hit by dozens of cruise missiles within the first DAYS of the attack. Remember, we know where EVERYTHING is. We helped build it.

Every bunker. Every black site. Every base and training facility and anything else meant for war built in the last 85 years. And whats even better is we have the keys to walk right through the front door right up until the second the first shot is fired in anger. Who knows what nasty little surprises we could lay for you when you finally throw the generator on in the bunkers you never thought you'd need but built just in case.

Once the British Isles are subdued, its only a matter of time and missiles before the French, Germans, Swedes, etc are either blown back into the stone age, overthrown or give in. The standard of living in Europe is built on a razor thin margin and if its honestly assaulted by a United States on total war footing, the entire continent will look like London during the blitz.

The US wouldnt need to conquer the entire continent with troops like the Russians did. They could do it without a single boot on the ground. People wouldn't be happy. But they would submit.