Climate change is projected to cause the average temperature of much of the United States to be above livable levels for extended periods. By 2100, it appears to be projected that large swaths of the American south will be uninhabitable for much of the year.
Because of this, I could see a mass exodus of USians from the southeast leaving their homes behind to move north. If not into the north of the United States, then into Canada.
Further, I speculate this event would wear heavily on Canadian politics, and be a sparking event for Canadian Fascism.
I could also see Alaska becoming Texas 2, with massive numbers of people moving up there… maybe they’ll try to secede too lol.