We violated that as soon as we started arming Ukraine, long before this war and even 2014:
...the United States, United Kingdom and France) pledged non-military support to Ukraine in exchange for its adherence to the Treaty on the Non-Proliferation of Nuclear Weapons.
...It refers to assurances, but unlike guarantees, it does not impose a legal obligation of military assistance on its parties...
It’s called a MEMORANDUM because the US Senate never voted on it, so like our “promise” of no NATO East expansion which we claim we do not need to adhere to, it’s just something someone once said but we are not bound by a official treaty.
Summary, we owe them nothing.
It's more like a handshake deal. We got Ukraine to give up their nuclear weapons. But basically, we told them that we got their back if the Russians invaded them. So here we are in 2024.
If we could go back in time, we would have told Ukraine to keep their nuclear weapons.