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...