The EU is a society that is winding down.
Americans are sensible and realize the future of innovation and progress lies in countries that have young people.
A bunch of old Europeans are not a threat. Europe is utterly feckless anyway and is unlikely to ever be able to field a large enough army to actually be a threat
In a list of American geopolitical concerns, a traditional force on force land invasion wouldn't even make it into the top 100. Swap out "Europe" for any other political entity real or imagined and it would make no difference.
Reminds me of that attempted mass murder at yet another Winter Festival in France - doesn't make any sense that this would happen again and again by Islamists from a US perspective, but from a "fuck it, we're just giving up" perspective it makes perfect sense.