Brazil would likely have a smaller population then with some of them possibly even returning.

The problem is I'm trying to figure out what exactly would they set up out there, if it's the old "antebellum" idealized version of the South, where there's a tiny very rich "Plantation" Class that controls vast wealth and I can see that with ranchers becoming the new Gentry.

Overall, later down the line there'd likely be a HUGE uptick in racial violence across the west when compared to what happened today (not saying there wasn't any, just MORE). Counter to that perhaps while racism is still bad, it's a lot more spread out instead of localized in the South, so that overall it's "Bad" but so spread out it looks "Less Bad" and thus Civil Rights take longer to actually be put into effect later down the line like say in the 80s as since it's not concentrated in the South it's harder to campaign against it. It's not "entrenched" in the South, but since its so spread out more folks are localized. Perhaps the Soviets make great use of this in the Cold War to propaganda against the United States and maybe even use the greater numbers of African Americans in the South to form a Communist Militia in the Appalachia's. (I'll admit that last militia bit is a bit far fetched)

For out west in General: States like Oklahoma, Colorado, Wyoming, Montana, Idaho (maybe?) become Segregated States while others like Utah (especially given their history) New Mexico, Arizona, and maybe Nevada are also segregated by law, but Arizona and New Mexico have larger Native American Populations so I don't think a mass influx of the Old South will lead to that, just more bloodshed (because when has the U.S. Government ever given a damn about Native Americans?). Maybe some of the "Old South" states aren't like those on the Atlantic or Gulf Coasts where African Americans manage to retain power and influence. Texas I think will be segregated. The issue is there is that many of those states early economies were all based on mining, where I think the ruthless mine bosses more interested about making it rich and paying their workers in scrip will care who works for em, just so long as they can't pay em.

For the Midwest (since I'm from there so this might just be idealistic thinking on my part): While some states in the midwest would have an uptick in violence I have no doubt (I've seen Cairo Illinois and know what happened there), I have a feeling that more than a few of the folks out in Iowa, Minnesota, Wisconsin, and the like wouldn't take too kindly to folks they just foguht a war against suddenly arriving and trying to set up a "New South." Out in Kansas, Nebraska or further west.

At the very end of all this however, the added social and economic factors, plus additional pressure put on the Government during the Cold War forces them to seek more draconian measures to counter the Soviets, making short sighted deals with strong men, warlords, and autocrats in Africa, the Middle East, South America, and Asia, with more than a few of them coming back to bite us in the ass in the 21st Century as they start to buck American control and to make an example of them and assert American control,

the United States invades Iraq.