He is not attacking them directly though, UK is pretty internally focused and won't really do much if the Ukraine operations expand and include to say other former soviet block countries.
In mainland Europe, France with La-Penne and Germany with AfD and now Sarah Wagenknecht[1] have far-right problems of their own and don't have political will for anti Russia stance so they won't be able do much either, rest of Europe are minor players or far-right governments like in Hungary under Orbàn.
[1] I refuse to call her party far left, now matter how she is described in media.
I guess that's the best case scenario right now. The worst case scenario is Trump pulling out of NATO completely, and (effectively or officially) allying with Russia.
I really hope I'm just not seeing all the pieces, and that such option is not even remotely viable, but it would be bad.
I'm quite sure the US will see a military coup, in the event that Trump tries to ally with Russia and become enemies with NATO countries. I mean, I don't think it is possible for Trump to pull out of NATO. Worst case is he simply decides to shut off all funding.
Politicians are short term, military officers are life-long and ideological.
With that said, NATO members (France, UK) have nukes. That's a line Putin can't cross.