Given that Canada will never voluntarily join the US—which it is adamant about—would Trump try to use force to annex it? And would Defense Secretary Pete Hegseth go along with this crazy plan?
No. Also, the US tried this in 1812 and it was extremely unpopular with the American public, even moreso than the Vietnam War. And while Trump has a lot of leeway not to act on foreign policy, Congress has considerable power to constrain a President's actions in terms of war.
John Bolton did an interview recently with Kyiv Post, which addresed this specific question of Trump WRT Canada. I think a lot of people would benefit from watching the thing. Bolton worked in Trump's first cabinet, spent a long time watching him operate as President. The two did not part on good terms. Bolton's an internationalist, for context, bit of a hawk, and supports NATO.
https://www.youtube.com/watch?v=O99JIvjq9t0
I really think that the interview is a worthwhile watch, but I can give a pretty short summary:
"Trump is not part of some sort of grand master scheme run by Russia. He just has very little idea about how government works, or how to accomplish what he wants done, and tends to operate largely in terms of his own personal relationships, which is not really how international affairs actually work. Either Trump thinks of you as friendly to him or not. Trump treats international affairs more-or-less as being how much he likes a given leader personally. He doesn't like Justin Trudeau, so he insults and snipes at Canada. Sadly, it doesn't go a lot deeper than that. The chance of an actual attempt to annex Canada is slim to none."
EDIT: I should note
Bolton has discussed Trump's positions on Greenland prior to this, to give prior material on the matter
that Trump actually does want to buy Greenland and that this came up repeatedly in his first administration, that he'd like it to kind of be his legacy for the US. Bolton points out that isn't new to Trump, as prior administrations have made offers to buy it. That isn't a joke. Trump just has no idea how to actually go about trying to buy the thing, and so is busily pissing off both Denmark and Greenland, which pretty much ensures that he can't.
EDIT2: Bolton did point out that he would say that Putin probably considers Trump to be an "easy mark", someone who probably would do a poor job negotiating and who can be manipulated.