Except that the non-american parts of Nato could easily end up not joining such a war. That could easily be considered something similar. All it takes is USA j

Except that the non-american parts of Nato could easily end up not joining such a war. That could easily be considered something similar. All it takes is USA joining a war due to defensive alliances with either japan or south korea. Then assume Russia joins the war on the other side, or already has joined it. Exactly what incentive do the European countries have to join such a war? They certainly wouldn't have any obligation (since Nato is also a defensive pact), and it would be a stupid idea to open a land front against Russia, because most of such a war would be fought on home turf due to Russia having more projective ability compared to Europe. Sure, Europe would probably eventually win such a war on sheer size of population and economies, but it would be a very very costly war.