Eliza C mentioned the popularity of River dance-Lord of the Dance- made me re-think my choice of Seegar. I can think of no sole representative or iconic figure. Maybe that is part of "folk."

Folk music has never been generally popular in the States and Canada. Even in the 19th century, composers like Foster and the minstrel lyricists were the rage. In my generation, only the Kingston trio and Harry Belafonte and his banana song made much of an impression on the charts (OK, the latter isn't folk, but most people think it is).

McCarthyism was vile, but even now, many years later, mention Guthrie and Seegar and from older people you get a questioning look and perhaps the question, "Weren't they communists?" Dylan, didn't he have something to do with hippies and flower people?
Burl Ives had a couple of hits, one a remake of an old minstrel piece, but the general public little noted the rest of his work.

Also noticed that Black folk music got little support here. The Negro spiritual perhaps had the greatest influence of any folk music on the public as a whole.