Most white Southerners migrated to America well after the Civil War. They settled the South and bug infested ares like Florida because the land was cheap.
The biggest racists I ever met were from the North! Did you hear me Yankee boy Jimmy?
I don’t think you’re correct about this. My understanding is that the South always received the fewest number of immigrants. Before the War because few immigrants wanted to compete with slave labor, and after the War because it was the poorest region.
Massive numbers of people didn’t migrate to the South until, I believe, starting in the 70s. Florida, of couse, is an outlier. Migration to FL started much sooner, the 20s, but interrupted by Depression and WWII, then resuming after the War.
I believe the South still has a much higher percentage of “non-ethnics” (silly term), often described as people of primarily English and Scots-Irish ancestry, than any other part of the country. Particularly in rural areas.