I don't think we're prepared at all. Sleeping elephant next door is having nightmares, and hopefully doesn't decide to roll over.
Fascism 101 requires an external scapegoat to domestic problems. Canada and Mexico are the prime candidates for that, particularly if your solution is militaristic.
Annexing Canada militarily would be a cakewalk. But Canadians would vote democrat. So it would only happen after US democracy is suspended. We're safe until then. Ish. There's an order of operations anyway. Mexico might fight back some.
You underestimate how many idiots there are in Canada too. Look at the prairies for example. The Conservatives who are basically just lite Republicans pretty much run those provinces and worship Trump too. So probably close to 25% of Canada's population would be ok with America taking over...
Yeah, I'd guess somewhere in the 10-30% range would simply accept it. I'm in Manitoba, which means more centre-left most of the time, except in farmland communities. I'd expect Winnipeg to attempt to resist somewhat, but fail.
Canada and Mexico will definitely be blamed for fentanyl crisis in America.
My feeling is that annexation of Canada is unlikely to happen militarily, they'd just use increasingly aggressive economic negotiations to turn us into a total puppet state instead of the partial puppet state we are now.
What would America gain from direct control of Canada? I guess direct control over more of the arctic. End softwood lumber 'subsidies'. Their corporations have pretty much free reign here.
I can imagine a fascist America occupying Mexican territory 'defensively'. And then waging a 'defensive' war against the cartels which results in more and more territory being occupied. But again, puppet state as the ultimate goal. They don't want to enfranchise Canadians let alone "Mexicans". (Scare quotes).