My honest guess is that the US has built remote shit into a lot of the heavy NATO weapons so if they were ever turned on the US they could be disabled or at least tracked. This would make repelling a US attack nearly impossible except where countries have maintained their own independent military infrastructure which is probably next to non-existent.

The US military can’t hold more ground than a military base anywhere though. They haven’t been able to since WW2 and even that’s being generous to them. Their whole MO is destroying and terrorizing a country in the hopes they succumb to the US’ whims. The US military cannot occupy or conquer foreign lands. So the US military could probably return Europe to the state it was in after WW2 if they wanted but they couldn’t meaningfully control it if the Europeans didn’t want to be controlled.

On the ground, maybe, especially as you get to more northern, colder areas.

Idk tho, Europe has nukes so that might come into play.

USAn is the best spelling yet, so close to UnSAne

They could easily defend themselves against a full scale US invasion — no question about it. The UK and France could kill around a fifth of all Americans in under an hour, which would probably cause the US to collapse. This is exactly why that scenario won’t happen and the US would use proxy wars and sanctions instead.