I thank you for your service, and can understand your beliefs on proper use of military force.I did say that. I spent two years in combat in Vietnam. What a fucking waste of lives and money that shit was. The US should protect it's shores and borders, NOT try to police the planet.
In any event, it's almost unanimous in this thread that the U.S. has no military role in a possible invasion of Ukraine. So why are you even arguing about that? At most, we'll support Ukraine with some modest weaponry but that's unlikely to play an important role in their defense against Russia. Everyone knows if Russia invades, Ukraine is fucked.
So the question is, can we even stop that from happening? As a global superpower, we can and should play a diplomatic role in trying to convince Putin not to cross a red line. We may not see that Ukraine has any meaning to our national defense, but they're still a fledgling democracy. If Putin can annex Ukraine without consequences, China will laugh because they know we would never stop a forceful invasion of Taiwan either.
Maybe we don't have enough leverage on Putin, but maybe he'll care that we're seriously considering treating Russia like a pariah state blocked off from international banking and finance. Honestly I don't know, but simplistically saying "not our problem" is incredibly short-sighted. When you're the only superpower remaining, some faraway problems are kind of your problems too.