How is N.C. culture shaped by east-west axis?

“In his famous 1997 book Guns, Germs and Steel [geographer Jared Diamond hypothesized that] along lines of latitude there will be more cultural homogeneity than along lines of longitude.

“To test that prediction, researchers at Stanford University used language persistence as a proxy for cultural diversity, and analyzed the percentage of historically indigenous languages that remain in use in 147 countries today relative to their shape. For example, the team looked at the difference between Chile, which has a long north–south axis, and Turkey, which has a wider axis running east to west.

“The researchers found that if a country had a greater east–west axis than a north–south one, the less likely it was for its indigenous languages to persist…. The result, say the authors, supports Diamond’s theory….”

— From “How geography shapes cultural diversity”  in Nature (June 11, 2012)

I couldn’t help wondering: Might this correlation even extend to the South?   That is, is some of the greater cultural diversity of North Carolina as opposed to Mississippi, Alabama and Georgia attributable to our east-west orientation?
Political scientist David Laitin, who led the Stanford research team, graciously agreed to  speculate:
“In principle, if we had data on persistence by state, we could test this. It might be neater to compare (a) the 13 colonies and California, both with N/S orientations; to (b) the South and the Plains, both with E/W orientations — with persistence of native American languages as the dependent variable.
“I bet you could get data for such a test, though with [values] n=4, I’m not sure we could do too much in the analysis!”