It’s probably a good thing I’m not a national leader because the first thing I’d do is recall all diplomats and cut off relations. He wants isolationism? Give it to him and let him feel it for real, not just his tough-guy head-canon version of it.

Use whatever human rights violation justifications necessary (shouldn’t be hard) to hit the US in the wallet. Cut off US businesses from customers abroad. Expel military personnel. Pull travel visas. All the tricks America uses against everyone else. Make the people feel the inconvenience of not being a world citizen.