Earlier quoted context omitted.
There's always been two Americas, if not more. We've just tried to fool ourselves into believing otherwise for a long time.
Then why did we fight a war on keeping them together. Maybe both would be happier if south and middle states split from coast ones.
https://fred.stlouisfed.org/series/FYONGDA188S
WWII being an outlier of course. I'd like to have the numbers for the 19th C.
There was a time when a state/county/municipality could largely ignore central government diktat. With centralization there'll be a tendency for a single dominant group to get into everyone's business more and more. This can happen via statute, spending, or even lack of law enforcement in desired behaviors.
..and of course it tends to split urban vs. rural, Anglosphere vs. everyone else. The wish or need for central control varies quite a lot between the groups.