General Discussion

Because Trump is not rational.

He seems to be in a "go big or go home" mentality right now.

So going for a tiny part of Canada does not seem to be his thing for the time being.

But yes he has started to talk about the borders being wrong between the US and Canada.
But I think he would go for a big piece of the border.

Yes if he sees it as personally beneficial to him, he will do it.

I do not know if there would be civil war or not in the US over a Canada invasion.
The American people, media, Congress, and judges are either enthralled with Trump
or sleep walking through life.