Edit: so apparently he thinks the American economy exists on its own somehow. That it is some behemoth that can't be stopped. When in reality it's quite fragile and those 3 countries alone could send us tumbling down the GDP rankings. Throw in the EU because of desires from Greenland and the US will look like the "escape from" movies back in the day with Kurt Russel.
They will suffer but not nearly as much as America. Hell, if Mexico really wanted to twist the knife, they'd nationalize our many many manufacturing facilities down there. I believe Canada has a few auto manufacturing facilities belonging to American companies as well. Just throwing that out there.