Given that one of the few good points of the Confederacy was their openness about negro inferiority, if the Confederacy ever did abolish slavery (whenever slavery as a farming method became obsolete, so around the '40s-'70s, if they weren't forced to abandon it politically) they would have no qualms about deporting every single fucking nigger a la Operation Wetback.
Of course, they'd likely be as powerful as Spain or Portugal who also chose to favor their agricultural interests over their manufacturing interests, but hey. Actually, that'd make them a prime target for a fascist-inspired government in the '30s… Hmm.
The North would have significantly fewer niggers too. In fact, they'd probably end up being 100% white.
If I had to do my own rendition of this, the likely changes would be that the US and the Confederacy would be locked into a series of on-going border spats as they both tried to claim the West, with by the 1880s the North being in control of most of it. Owing to the North's far better industrialization, the South would probably come off the worse in most engagements a la Franco-Prussian War or Spanish-American War, but their expansion southwards would be basically unchecked. Owing to a divided America, there will probably be a series of minor wars with Britain trying to take back the colonies. Nothing much is likely to come of it; perhaps a small amount of territory changing hands several times. By the 1890s/1900s the US will still almost certainly have eclipsed Britain as the world's manufacturing power, but will probably not have so great a lead on them and Germany. WWI has a more uncertain outcome; US entry into the war is unlikely to happen owing to the conflicts with Britain and paranoia about the Confederacy. If the Confederacy hasn't been turned into a British dependency by this time (very likely to happen) it will have extremely close ties to Britain but nothing more meaningful strategically than acting as a check on the US in the Americas, creating the same encirclement situation for the US as existed for Germany. Owing to the, by now, clear position of military inferiority the South is in they are unlikely to start any wars with the North, but they'll serve to stop the US getting any ideas. Britain, getting into a worrying state over Germany, might try to woo over the US and alienate the Confederacy, while the US is likely to be isolationist x1000. WWI almost certainly goes on for years more as the Germans make fantastic gains in 1918, perhaps even forcing a French capitulation in 1919 or 1920 and ending a war in a stalemate with the British, most likely because of the emerging Soviet threat that convinces the Germans not to prolong the war. Without Western intervention in the Russian Civil War the Soviets seize total power more quickly and have a stronger position. They will probably launch some sort of attack on the Austro-Hungarians who are nearing collapse, and who probably will collapse under one of the multiple (((communist uprisings))) that are sure to occur. Germany will thus find itself in a panicking state amidst a destroyed Central Europe against the Soviets. The Great Depression will probably be especially severe in France and the Confederacy. Fascist governments will likely take power in Spain, Portugal, Italy, and possibly even the Confederacy and France. There might even be a French civil war with (((leftists))) trying to seize power, though it is not clear who would support the opposition. Germany might send troops to France and Spain? Britain might. It's not clear whether there would be a civil war within the Confederacy and whether US troops would attempt to do anything.
What is clear is that the whole of the 20th century plays out very differently. I'm not even sure what WW2 would be like/whether it would even happen. Would the Soviets be destroyed? What would happen to the Germans? Does the Confederacy undergo a large amount of growth throughout the '40s, '50s, '60s, and '70s to finally become industrialized? Do any superpowers emerge? Does leftist bullshit come into fashion and does it get pushed by any superpowers? What of decolonization? Does the US go retarded and ruin its (this time) pure white ethnostate, perhaps to ideologically oppose the Confederates? What happens to Britain?
