There is the theory that President Trump is still bitter about his Canadian hotel ventures that went bust.
Some, on social media, have speculated that a 2019 photograph in which Justin Trudeau appeared poised to kiss Melania Trump, the first lady, at a Group of 7 gathering in France, left Mr. Trump with a grudge against the dashing Canadian prime minister.
And then there is the transactional view, that Mr. Trump sees the acquisition of Canada as the 51st state as the ultimate real estate deal that would seal his presidential legacy.
