In America, there is an undercurrent of resentment in some groups toward NATO and the EU. The US spends a lot of money on them, and is expected to risk open nuclear war with Russia, for the sake of Europeans who are never grateful no matter what.
Of course, it's not like the US has a spotless record on international affairs, but is Europe really strong enough? I think so. The fact is, if you need the US to prop up your defense when the US spends more on its military than the entire Russian GDP, something is off.
Putin knows attacking Poland, Germany, etc. would unleash hell. And he can't even conquer Ukraine.