Eh Buddy Hoser

Don't worry, there's no way that the US wouldn't make it Europe's problem if he started invading other nations.

He could only invade Mexico or South America without triggering article 5. Since Canada and Greenland (through Denmark) are both NATO members if he messes with them then its immediately a good chunk of Europe's problem. There's also French Guiana in South America and some islands in the carribean I forgot when I started typing that would also trigger article 5.