Well, folk music has been mostly urban in the US since the "folk scare" revival of the 1950s and 1960s; but most of the truly Enlish-language traditional songs the collectors collected, came from rural areas. Could it be that the true urban folk music of the U.S. was the music of immigrants?
I think it's safe to say that folk music has not been a commercial entity in the US since 1975. There are active and flourishing folk clubs in a number of U.S. cities - but with a few exceptions, people generally sing in living rooms, not in pubs.

-Joe-