Other than the San Juan islands, there are no territorial disputes between the countries. The Canadian military is utterly dwarfed by the USA's, so any aggression on their part will likely result in a total loss. And if the USA really wanted Canadian territory, they could probably ask for it and be granted some in a popular vote (at least in the south western provinces).
Even if China and Canada become besties, China still can't do anything militarily. Canada is still gigantic; protecting the east of the country is impossible. And it would be straight forward for the USA to deny access to the Atlantic.
Yeah, the US government would not at all like the idea of China stationing troops or missiles in Canada, but Canada would see the stupidity of allowing such a move long before it came to pass. And if they didn't, the USA has diplomatic options (mainly, "hey, BC/Alberta/Sas, u wanna b american? :cowboy:"). Getting one to come to the red white and blue side effectively divides the country in half.
He has no interest in fixing any relationships. This is a war of genocide. Things are only getting started, and the sooner the world realizes we are already at war, the better.
This is what is actually happening. It is a crime and I wish Putin, his close circle and other directly responsible would end their days rotting in jail.
As for Canada turning into China and hosting their nukes. Of course this will never happen and is absurd. But in pure hypothetical world I am pretty sure the situation like this will turn into invasion if all negotiations fail. As a mini example see what happened when Noriega had started switching his allegiances from the US to a Soviet block.
Hm... Not quite. Noriega began switching allegiances to the Soviets well after the relationship with the US became hostile, and well after the US made it clear they want him gone, due to Iran-Contra and other reasons. He was also a dictator who lost an election by a factor of 3 to 1 a few months before the invasion. Bush was still hesitant to invade until a group of unarmed off-duty US soldiers was attacked, one of them killed and others abused in custody. Not defending the idea of propping up dictators or invading countries to remove them, just that this is not a good example of the point you're trying to make.
Most likely by reflecting on what went so horribly wrong in the relationship with Canada that a formerly closest ally of them all has decided to turn to a different power from across the ocean for help. Then, by attempting to fix said relationship without starting a futile and criminal war of aggression that will cement multi-generational hatred of all things American north of the border.