I kinda expect the EU to go collective defense if the US pulls out, to see if the US can still be trusted to honor its words, of if they have to write it off entirely (honestly, they should have done that before, but…)

I don't see that.

Netherlands, Austria predominantly leaning right now, joining Hungary, Slovakia.

Germany and France are both with very unstable governments.

Pretty much leaves Poland and the Baltics

I don't think they see an unilateral suicide as more tempting than a bilateral suicide.