No involved; none of our business, not a security risk to the US, this is more of a civil war than anything else. Total waste of American money and resources.
it is pretty normal to see small fighting between successor states of collapsed empires in decades (and even centuries) after separation.
of course, here if the US wasn’t basically funding and running the UKR military including who knows how much hands-on help, there wouldn’t have been a war. it would have been over very quickly.