China considers participating in peacekeeping forces in Ukraine

Greenland and Canada aren't about countering a Russian military threat. Both are NATO members with US bases in them. The Russian threat to the US was much larger during the cold war and yet the US didn't annex them back then. This is about force projection in the arctic. Control of both the NW passage and the Panama canal would increase US leverage on the world stage, including on their so-called allies. Local resources are most likely of interst as well. Even then, I suspect that a large portion is just rhetoric to stoke up visions of grandeur and might among his supporters, since that would track pretty closely with how fascist regiemes have operated in the past.

I admit that "current de facto US ally #1" might be a bit strongly put, but it's not like the bar would be too high at this point. They do get along well enough. Putin isn't dumb enough to antagonize the US president who is more useful than any of his predesecors in a long time.

A NATO occupation of Russia, be that through overt means or a friendly coup, would still be incredibly expensive and thus politically unpopular across the board. Also Trump is all about pretending to be the peacemaker when it comes to Ukraine and Russia, so this would never go forward barring a major restructuring of NATO where the US is booted out or at least knocked down a peg from their current hegemonic position. Both seem unlikely to say the least.

The way I see it, China is just trying to position itself as a force for reason and making the most out of recent US shortcomings in soft power projection by exercising its own to fill that vacum.