Do people in the United States wear face masks outdoors?

Most reasonable people do. The ones who don’t comply are the ones that would probably wear a confederate flag as a mask.

when they are in public places but not like in their backyard.

I don’t wear one outside but inside stores and public places I’ll wear one. 

Yes, here in the United States it is a requirement to have a face mask when entering most public places. If you don't wear one, they can refuse you service and make you leave. 

Not usually, unless they are going in and out of a building.

Only the sheeple.

The dimwits do.

Some people do.  I don't.

The Koreans in my town have always worn facemasks outside even before covid.