I think you will find that the liberal-capitalist world order with some semblance of norms like national self determination and resistance to overt nationalistic annexation does benefit the US.
Note that I’m not saying I like this world order, or the US politic. But your assertion looks false to my eyes. Even if there was no moral issue of enabling Ukrainian self defense because Ukrainian self defense is a moral good, the USA benefits from preventing authoritarian regimes from using military force to swallow up their neighbors. And so do the European countries.