If Ukraine falls then the Baltics will be next - I can see Poland, France and the UK attempting to help but I suspect this would ultimately fail leading to the breakup of NATO. EU either breaks up or becomes much stronger...
If Poland France and the UK are more invested in opposing Russia then one would think that the Ukraine wouldn't be entirely reliant on the US to support it. This is the fundamental problem with the proxy war in the Ukraine, the people pushing for it talk about it as if the fate of the European continent rests on the fulcrum of the Ukraine and yet the other European countries hardly seem to care.
In practise, doesn't that depend on what the US decides?
This is a threat Trump has made openly and repeatedly.
If USA pulls out it’s likely that EU will shift some of its aid over to military. This is already happening: European countries have started setting up arms production within Ukraine which gives Ukraine more guns per dollar spent than what donations of western built weapons does. So don’t think the dollar amount donated tells you everything about the amount of military support given.