I think a material difference between Iraq (v2 anyway) and Ukraine is that they can keep doing the "well Russia was the aggressor" thing indefinitely even if the reality is more complicated.
also yes obviously some libs are still stubborn about Iraq, the worst ones, but for the most part its generally agreed that the Iraq War was a bad thing.
I think the difference there is that many liberals were against the war in Iraq, but no liberals will go against The Troops. They may not always like what the military is doing, but they will always gleefully vote for funding their every wish.
also almost none of them were against invading afghanistan, so the fact that about half of them had some reservations about the 2nd front opened up in bush's reactionary crusade against the middle east says NOTHING when you consider that they rally behind him right after 9/11 when ultranationalist fervor was at a fever pitch in both parties, the crucial moment when destructive wars against countries that didn't attack the United States needed to be opposed the most.