I think its more the same as Americans aren't a part of their military. So after the initial rush of the invasions and the occupation set in with no exit plan the conversations about the "cost" of the occupation in lives and treasure could be heard.

General economic sentiment in the USA for the average person is pretty grim, seeing a headline about how 113 Billion Dollars is being spent on the War in Ukraine and wondering why some of that money couldn't be sent "my" way, is a very real thing. Then seeing the headlines about the all the fancy million dollar whizz-bang toys getting blasted followed by ANOTHER headline about billions being spent on Ukraine can't make anybody happy.

In Ukraine, they (officially) don't have boots on the ground. I could see the resentment stem from "we gave them every Wunderwaffe we had, and they still lost reeee!", but surely this will be blamed on "bloodthirsty, savage invaders"

I'd bet more on us Yanks, as a people, just not caring enough to remain emotionally engaged in this conflict. It won't matter if its Ukranian incompetence or the bloodthirsty invaders, none of us have any reason to get worked up over what's going on over there.