Thanks for the laugh, most Americans you describe never travel further then NA lol.
Around 40 million a year travel overseas.
Around 15 million visit Canada.
Around 32 Million a year go to Mexico.
~ 15 Million a year go on a cruise.
Etc etc. All of those involve leaving the USA for a foreign country. A foreign country that is totally within their rights to tell them they're not welcome if they present a serious potential health threat to said country.
I think you underestimate how many and how far many US citizens travel.
We just went through this last week. Trump wants to open the border again. Canada: We don't want you, piss off.