What does it mean to say "English folk songs were not exported to America"? Does it mean, the stuff that popular 20th Century versions on the Hit Parade is more often Scottish or Irish than English? That disregards tradition focuses on contemporary pop as the only kind of "folk music" somebody ever heard of, which is sort of annoying. I think the rule is, traditional English songs went to New York and New England in the 17th and i8th Centuries and are still sung there. Scottish and some Irish songs traveled to Appalachia in the 18th Century, and strictly Irish songs mostly went to the cities, in the 19th and 20th.