Lol I believe soviets signed the same agreement “protecting” ukraines right to exist, but shush dot bring that up
Whether the US senate ratified it or not is irrelevant.
It’s a signed Memorandum between multiple heads of state, whose provenance is derived from the Belovezha Accords and the Helsinki accords. And the United Nations Charter.
Ukraine, like all ex Soviet states, had its “independence, sovereignty and territorial integrity” guaranteed in writing. The USA has no right over it, nor does Russia.
The USA and Russia, along with the UK, merely reinforced existing provisions.
Russia wanted a freebie from Ukraine - its nukes. Ukraine said “quid pro quo, we’re not going to disarm without watertight security guarantees”. Russia said “okay”. USA and UK also said “okay”.
There’d be no issue if Russia had stuck to the agreement instead of repeatedly violating it.