What is the endgame plan with Canada?

With Trump and some of his base floating talks about annexing Canada, to enforcing tariffs on Canadian goods, Im struggling to understand what exactly it is that Trump is trying to accomplish with Canada.

Is he actually serious about trying to make Canada a 51st state? Why are we imposing tariffs on Canada? I can understand tariffs on a country like China that has used cheap labor to steal manufacturing jobs. But has Canada done the same? If tariffs are instead being used to gain concessions, what exactly is that?

Basically, why are we picking a fight with Canada and what wrong have they done in the past to justify this?