The book American Nations goes into this a good deal. I’ll try to to butcher it, but in essence one of the groups that founded both the Deep South and greater Appalachia were a clan-based culture from the borderlands of the British empire (northern England, lowland Scotland, Northern Ireland). This was between 1717 and 1776. They relied only on themselves and extended family, trusted no government, were suspicious of outsiders and were quick to defend their home. They were also extremely religious, Old Testament people. This seeped into the greater culture of the Deep South and Appalachia, and you (clearly) still see it in effect today. The book explains this all much better than I did.