Canada is purely posturing for trade negotiation purposes. Adding multiple states and the population of Canada onto our voter rolls and political system is an unrealistic logistical nightmare. Republicans would be insane from a balance of power standpoint to even risk such a thing. He isn't going to annex a NATO member, and they won't come willingly for the most part.
Greenland I believe is a great deal more likely. He has talked about purchasing it historically, and the idea has been floated in the past outside of the Trump sphere. Would be a terrific "vanity" acquisition for Trump to cement his legacy while being a great deal less consequential than Canada. They won't ever be made a state in the near future with a population of 60,000, a tenth of Wyoming. I could see a deal being reached with Denmark, either for outright ownership or increased partnership.
He won't use military force, in either case. That's purely a bluff to not take any cards out of his hand.