Actually, you're wrong ...
The "Budapest Memorandum" - with signatories Britain, USA, and Ukraine - was signed by Clinton in 1994, in which we agreed to provide military protection in the event of soviet aggression in return for the Ukraine dismantling its nuclear weapons. This Memorandum was updated in 2010 by Obama. No words were formally put in there about withdrawing the NATO application, but that was what led to the update. Frankly, even without the update, we committed to providing them support under our umbrella.
Further, the European Union - Ukraine Economic Agreement, originally signed in 2010, and reiterated in June of this year, clearly states the agreement of cooperation and mutual protection under UN Resolution 1373 (Global Counter-Terrorism). Section 4 of that document was very explicit about the commitment to provide mutual security support.
I'll quote the executive summary: "In cooperation on justice, FREEDOM, and SECURITY (my emphasis), the Parties shall attach particular importance to the consolidation of the rule of law and the reinforcement of institutions at all levels ... " "Respect for human rights and fundamental freedoms will guide all cooperation on justice, freedom, and security. "
But, I do love your waffling ... "well, yes, we said it, but that doesn't count ... if it isn't in writing, it ain't true. My word, my honor, means nothing ... only thing that matters is what you can prove in court. My word is NOT by bond."
That IS what you meant, isn't it?