As poor of a state that is Europe's various armies, I'd be very surprised if EU couldn't take on Russia even without the US (who FWIW recently reiterated their commitment to the defense of Europe). Russia's advanced SAMs, radars, and Navy have seriously deteriorated. Their main capability left is submarines and mass Shahed drones whose range can't reach much of Europe.
If Russia's jets can't operate over Ukraine they won't do much in Europe except self-defense of their own homeland.
China on the other hand is a very very serious opponent...
Russia's advanced SAMs and radars are getting clapped by one of the poorest nations in Europe. We're at almost four years of full scale war and the worlds no. 2 military has not been able to get air superiority over a small airforce of cold war left overs. Just the airforces of the Nordic countries alone would run rings around the russian airforce and their air defence.
If Russia's jets can't operate over Ukraine they won't do much in Europe except self-defense of their own homeland.
China on the other hand is a very very serious opponent...