Does an informal representation to the head of a government that is now defunct as to the intentions of a President and Secretary of State who are no long in office bind the the US and their successors in office? Nope. Not one bit. Not legally, not morally, and not in any practical sense.
NATO during the Clinton regime bombed Serbia for almost three months, and today discusses putting "peacekeeping forces" -- i.e. military troops -- in Bosnia-Herzegovina, which is not as yet a NATO member. Parsing the "who said what to whom" is all very nice, but "not legally, not morally, and not in any practical sense" also applies. To both sides, however one determines the sides to be. Given the potential of BRICS, as billions in population, move away from the West in terms of banking and more, "practical sense" seems MIA. What is certain is that Biden most recently said the US must "lead" the "liberal world order." Not my choice. I do want a "leader" to being with. "...in any practical sense."
What practical sense does the US have in funding or defending Ukraine?
You can’t expect other countries to live up to past agreements or treaties and exempt your own country while declaring yourselves morally superior because it is okay when we do it. If those promises to Gorby can be ignored now, then so can the border in Ukraine.
The current US regime doesn’t even honor the Constitution or the rule of law. Moral superiority? What a joke. The current regime even bullies it’s own supposed allies? Moral superiority? Nope