Again, in a legalistic sense, sure.

But again, in a legalistic sense, even NATO Article 5 also doesn't obligate the US to do anything.

No document (Budapest memoranda or NATO treaty) can require the US to do anything, so all that matters is whether the US is signaling itself as a country that defends its partners.

If you believe that Article 5 obligates the US to do anything more than what we've done so far in Ukraine, please explain why.

If you don't believe that Article 5 does that, then I'm not sure why you seem dismissive of the idea that we're creating conditions for a nuclear proliferation spiral.