IOW, we screwed Ukraine and deceived them to give up their nukes, and now they’re being invaded by the Reds and it’s not our problem.
"We" didn't screw Ukraine. The only way that "we" do anything is by treaty in accordance with our Constitution, and "we" never did such a thing regarding Ukraine. I believe that if you study the Budapest Memorandum carefully, you'll understand that it was neither intended nor represented as a military commitment to Ukraine. But even if it had been, our Constitution trumps the unratified signature of our head of state.