Even though Ukraine isn’t the most wealthy of countries, the last thing I want to see is precidant for invading other countries like what they did to Moldova or Georgia. There has to be a line somewhere. Ukraine truly wants to stop Russia right now and the US benefits from removing a strategic competitor, acquireing new tactics and knowledge. Believe me, there’s a lot worse that the US and European governments can spend money on (and absolutely do)
I have a moral argument too, but that’s for some other time. I get that it’s hard to sympathize with a country half a world away though.