How would any number of nukes protect Canada from a country with over 5,000 of them.
Just the threat of a few nukes taking out DC or some other major city is usually enough of a deterrent to not start shit. Yeah, they could litter Canada with ground zero zones, but that's not the point.
Trump is a different animal though. Most humans care about other people so the threat of a country nuking New York or DC is a pretty good reason to make political arrangements this doesn't happen. Trump hates humanity and only cares about himself. I honestly think he would be in heaven if a nuke took out LA or Portland.