I think one can safely say that the failure of NATO to defend one of the member countries, in the case of a military attack and invasion would clearly lead to the collapse and dissolving of NATO as a military defense organization, since the core purpose of NATO is precisely that — for — the member nations.
It's a nice theory, but that's not happening. The purpose of NATO isn't mutual defense - it's to bind Uncle Sam to Europe's defense. Europe will stay in NATO because it offers a security blanket, and the alternative is to spend big bucks on defense, which they can't do without either destroying their economies or dismantling their cradle-to-grave welfare states. Nope - they'll hit the snooze button and hope that Uncle Sam comes to the rescue when the next NATO member is attacked. They are just Eloi being Eloi.
The problem they have is most of their Parliament left and would not serve under those who assumed office...so they have no “controls” on anything in needing experienced managers of....They're even advertising on line for people to take positions! I think Ukraine is definately going to get the short end of the stick, and their high expectations will take a blow as they see more and more the EU drag their feet in assisting them.