What I find un-realistic though is CS of America allying itself with Nazi Germany.
This is a popular notion that seems to be common in any alternate-history book about the south winning the war, which is IMO very anti-Southerner.
You must remember that both the people of the south, and those of the north, were Americans. They shared similar ideas regarding democracy.
Sure, the north was anti-slavery and all, but other than that, they were both Americans. And racism in America was far from dead even long after the war was ended. Actually, I think the 1950s were probably the worst years to be an Afro-American in whole of the the US - north and south.
So, just as the south was democratic as the north was, and as racist as the north was

, I think that even if the south would have won, America would have never allied itself with the Nazis.
Most likely American economy would have been backwarded because of agriculture conservatism, and social rights would have took much longer time to thrive than the real America, but overall - I think they US would have stayed the same. Maybe just slowed in it's development a bit.