You asked about American interests in Ukraine. Here Sen. Cruz delivers a floor speech explaining American national security reasons for supporting Ukraine: https://youtu.be/fv3iGHRZyys
That's the most profoundly stupidest speech I've ever heard.
The fact of the matter is that we actually provoked Russia into preemptively attacking Ukraine. NATO should be obsolete. There is no need for it. Also, Ukrainians are literal Nazis with the most corrupt government comprised of nothing but beggars and thieves.
If Putin somehow ends up losing the war and therefore has nothing to lose, this will escalate into a nuclear war and he will retaliate against the U.S. America is the country fighting the proxy war against them. America is also responsible for destroying their Nord Stream pipeline.
Putin is a demagogue, but non intervention is the best policy in this case. Unfortunately, the U.S. is largely responsible for manufacturing this conflict so the military and financial aid will continue and that's a huge detriment to America.