> Many people believe that the US annexing Canada is a higher probability than either China or Russia doing so. All three are very low probabilities.

I believe those people are being a bit silly, and their position probably comes from a strong dislike of Trump as a person, and not a genuine belief.

Russia annexed a warm-water port and then shortly after attempted to incorporate Ukraine as part of a plan to remake the USSR. The only thing keeping China from taking Taiwan is the United States.

The US has no desire to annex Canada, and it also has no need to. If Canada proposed statehood or even a territory agreement with the US, I genuinely don't think it would even pass a vote.