I don't see anyone in the above posts who could be compared to Ralph Peer. I don't believe there is anybody.
Correct me if I am wrong but it appears to me that the UK collectors were working from a scholarly viewpoint as was John A Lomax in the States. Some with a view to using ideas from traditional material to be integrated into their own compositions. With Ralph Peer it was purely commercial. His deal with Victor records was that he got all the publishing rights on material that he recorded. The American labels thanks mainly to big sales of a recording by Georgia's Fiddling John Carson realized that there was a big demand for this rural music in the south and in areas of the industrial north which were a magnet to workers from the impoverished south.
Peer having the publishing rights encouraged the musicians that he recorded to use(supposedly)non copyrighted material or write their own material. Some of this turned out to be re-written/adapted older published material. It's therefore very largely due to Peer and his commercial ideas that such a large amount of old material was saved for our appreciation.

Hoot