Joe Offer makes a very interesting point, I think, when he says, "if the Puritans executed witches, don't you think they must have believed in supernatural witchcraft?" He's right, of course; many people of that time (Puritans and Cavaliers alike) believed that witches could harm others by casting spells.
Since the Puritans did believe in witches, one might expect that, even as the Elvish elements faded from the old ballads, the theme of witchcraft would survive, at least in New England. Maybe it did. (Where are the New Englanders when you need them?)
In the Southern Appalachians, there is hardly a trace of witchcraft in the oldest songs. In Patrick Gainer's FOLK SONGS OF THE WEST VIRGINIA HILLS, there are 50 Child ballad texts, but not one has a witch. In Leonard Robert's SANG BRANCH SETTLERS, Mr. Roberts collects several stories involving witches from his sources, the Couch family of Eastern Kentucky. He also collects texts of eight Child ballads (#s 3, 53, 54, 81, 84, 95, 274,and 278), but not one has a witch. I don't know why.   

P.S.
Joe Offer, I didn't mean, when I described Puritans as "liberals", that they were liberal in 21st Century terms, as if Oliver Cromwell had been attempting to nationalize medicine or get the troops out of Iraq. I meant that they were the liberals of THEIR day, the ones who wished to accelerate the trends of their times, rather than slow or reverse those changes. Of course, some of them were, on important issues, liberal even in OUR terms. On the issues of preserving the monarchy and preserving the Established Church, John Milton was to the left of Tony Blair.   

Kent