Mechanization: You totally dissed this one, saying that blacks would be needed to operate the machinery. Perhaps, but a plantation that once required 100 slaves would now only need 10. Mechanization on its own would at least cause slavery to shrink.
Popular feeling and opinion: The majority of people worldwide did not approve of slavery. The majority of Southerners were for gradual abolition. Did you know that there used to be more abolitionist societies in the South than in the North? That was before Northern abolitionists made themselves obnoxious by referring to the south by all sorts of foul names and calling the union with the south a compact with the Devil. It can be argued that the vitriol coming out of the North actually delayed slavery's demise by causing Southerners to take offense and stick by their guns on something they wouldn't have otherwise fought over.
Even so, the South would likely have abolished it around the time that Brazil did. If the South had won the war, Lee (among others) would have been a very prominent, respected, and persuasive voice urging for emancipation.
That was in 1871, only six years after the USA's bloodiest war, fought to the bitter, bitter end by slave-holding leaders who refused earlier surrender if terms included abolition of slavery.
So I think not.
Consider: Since Robert E. Lee died in 1869, he would certainly have no influence over any such debate in 1871.
But Confederate President Davis lived on until a few days short of 1890, and would certainly have a great & continuing influence.
Confederate Vice President Alexander Stephens, who delivered the notorious Cornerstone Speech on March 21, 1861 -- he lived on until 1883.
And let's look at the great Southern Fire Eaters:
Add to those hundreds of thousands of Confederates veterans who fought & suffered to the end, and had that end been victory, would certainly not wish to give up the very cause -- slavery -- so many others died for.
Finally, it's important to remember that slavery's defeat in the United States had a profound effect on other countries, especially Southern America, such a Brazil.
Had slavery and the Confederacy proved victorious in the 1860s, there's no reason to suppose others would be in any hurry to abolish it.
DeoVindiceSicSemperTyrannis: "Mechanization: You totally dissed this one, saying that blacks would be needed to operate the machinery.
Perhaps, but a plantation that once required 100 slaves would now only need 10.
Mechanization on its own would at least cause slavery to shrink."
Possibly, but remember that, for the most part, slaves could fully take care of themselves.
When they were allowed (which was not always) to grow their own crops & livestock, the cost of their upkeep was nearly zero.
So, if it took, for example, 100 slaves to run a small plantation, why ever would the owners invest in expensive machines which would only do the same thing their already paid-for slaves were doing for virtually free?
In a slightly different form, we see this exact thing today -- in places where migrant farm workers are available and cheap, they are used.
Where migrants are not available, farmers sometimes invest in machinery to do the work.
So I'm saying slavery would have delayed the introduction & success of labor-saving machinery.
And one other key term to remember: "filibustering", which in 1860 did not mean speechifying in Congress, but rather referred to adventures young men put together to conquer & rule over Central American countries.
They were generally unsuccessful, but their idea was to make new lands available for white settlers and their black slaves.
They hoped a new Confederacy would provide for, in effect, state-sponsored filibustering.
Such conquests would lead to slavery spreading anew throughout the Americas.
Botton line, my point is: had the Confederacy proved victorious in Civil War, the world afterwards would become a very different place than it, in fact, became.
One pro-Confederate wet-dream on the Confederacy's future "history" conquests: