Europe is running into a problem where American participation in European affairs has gone from guaranteed to not guaranteed, which is exposing the weakness of Europe's militaries.

You have some decent military powers in Europe, like France and Poland, but most countries have a token force for defense that is poorly funded and poorly maintained.

Logistics for most militaries has depended on American support, whether it be for materiel or moving forces and materiel across the continent. People have been joking about Russia's dependence on rail for its military, but I doubt European militaries have better options.

Finally, the USA provides a lot of high level of support to European militaries when they do act. This includes signaling, intelligence, and some command & control assistance. France has some of these capabilities, but no where near the level needed to lead a war between Europe and a near-peer.

So Europe got to enjoy its peace dividend and now it's freaking out since it needs to start building the kinds of institutions that America built for them.