No stupid question… it seems Trump is ready to invade (military) Panama and Greenland (red white blueland), so even if with Canada he always talk about economic war and annexing Canada blablabla…
What would happen if USA invades Canada? What would be the reaction of the Canada King (Charles III is the king of Canada)? The Commonwealth? NATO?
Practically speaking since war is unthinkable is would result in as much economic isolation as Europe can bear. It would be the end of NATO. Almost immediately there’s be European voices saying ‘What’s the real harm?’ and other appeasers. I think the political lash back would only last 5-10 years as parties opposed would find the only tool at hand - economic punishment - to be unsustainable. It would legitimise nationalistic sentiments in Europe even further. Britain would, naturally, talk of betrayal but not be able to make any resistance of any substance.
It would be an invasion and occupation. Very very few Canadians would cooperate with the annexation, and more than likely it would look something more like Afghanistan or Ukraine, but with much better equipment being provided to resistance forces.