> the [antebellum] American south was probably the most advanced agriculture civilization ever

I don't follow. Certainly the current farming system in the American mid-west is orders of magnitude more productive. But even if we're focussed on pre-industrial history, are you sure that the ancient South American agri-economies weren't better? And for productive land use, what about Japan and south-east Asia, where every square inch ran like clockwork.

I'd like to see a citation for that. Everything that I've read up to an undergraduate level implied that their farming methods were less than ideal, even by the standards of the day, and that in many ways prime land had been exhausted.

Tennessee originally wanted to fight for the North and much of Western North Carolina didn't want to join the confederacy because most of the people in these regions owned no slaves and were rather poor Irish, Scottish, etc. immigrants rather than aristocracies and industrial tycoons like a lot of the Deep South and didn't see any benefit to supporting slavery. However, they did always wonder what'd happen if they didn't join the rich Southerners and the union lost. There's a lot more factors obviously but lumping in Appalachia with the south is an oversight that is pretty misplaced.

Tennessee and much of Appalachia has been historically on the side against slavery and corporate interests until somewhere around 60 years ago. I don't know how it happened besides hand-waving "Southern Strategy."