The war requires an ideological foundation for support, so the US has gone with it's classic "defense of liberal democratic ideals." It would be much harder to give a shit about Ukraine if the war was viewed as a beef between two reactionary states. The invasion would still be alarming, but people might be willing to forego the Ukrainian state as currently constituted if it lead to peace and the preservation of life. The wholesome smol bean democracy discourse is essential. It turns the war into an existential global crisis as far as liberals are concerned, and turns any compromise into appeasement. The fact that all left-wing parties, media, and labor unions have been banned, all elections have been postponed indefinitely, and that the country is effectively under martial law doesn't matter. It is a "democracy," and the ideal is worth defending no matter the cost in lives.