A great many of the early settlers in the Appalachian region of the U.S.(where much of America's folk music and culture was formed) were devout Scots-Irish protestants.* To this day that part of the country is perceived to have more than its share of religious fervor.

*from Wikipedia:
The term "Scotch-Irish" is an Americanism, almost unknown in Britain and Ireland, and refers to Irish Protestant immigrants from Ulster to America during the 1700s. An estimated 200,000 or more Scotch-Irish migrated to America in the 18th century.[2] The majority of these immigrants were descended from Scottish and English families who had been transplanted to Ireland during the Plantation of Ulster in the 1600s.[3]Scholarly estimate is that over 200,000 Scotch-Irish migrated to the Americas between 1717 and 1775.[11] As a late arriving group, they found that land in the coastal areas of the English colonies was either already owned or too expensive, so they quickly left for the hill country where land could be had cheaply. Here they lived on the frontiers of America. Early frontier life was extremely challenging, but poverty and hardship were familiar to them. The term "hillbilly" has often been applied disparagingly to their descendants in the mountains, carrying connotations of poverty, backwardness and violence; this word probably having its origins in Scotland and Ireland.

The first trickle of Scotch-Irish settlers arrived in New England. Valued for their fighting prowess as well as their Protestant dogma, they were invited by Cotton Mather and other leaders to come over to help settle and secure the frontier.