What if a NATO member is suddenly hostile to you and Russia says it can help you? Russia probably does not want the US to have Greenland.

It would certainly trigger a collapse of NATO. But if the US is serious about taking Greenland, that automatically starts the collapse anyway, right?

Anyway, just all hypotheticals. Interesting to think about. I don't think chances are 0. History has shown us that countries make surprising decisions, including allying with historic enemies, when pushed against the wall.

Well eventualy one would hope the Putin Mafia dies out and the Russian Diaspora manages to turn that country back to a happier place than its current child-abducting state. There are many good russians, there is an actual society under the madness, look: https://www.youtube.com/watch?v=9_0E9IzXT34