There are interesting side-speculations about what might have happened to America had we not fought the Civil War which do not concern themselves with slavery and race. They don't get much air play, because they're pretty much totally irrelevant to the question of whether we should have fought; but they're still kind of fascinating. For example, what would trade policy have looked like if the Confederacy had left us?
One of the big issues between North and South, after all, was the level of the tariff. The north wanted high tariffs, to protect its industries from competition; the south wanted low tariffs so that its farmers could buy cheap manufactures. Had we not reconstructed them into the Union, we would have lost the major constituency for free trade in Congress.
It's an interesting question. Had we not ought after Ft. Sumpter was attached... I think that war would have eventually been inevitable. The north and south would have continued to expand west, which would have led to more "Bleeding Kansas" type scenarios. Also, it would have opened up the possibility of more states defecting (i.e. the South would have set a precedent). What would have stopped New England from defecting if they didn't want to be taxed for their profitable mills and whaling industries? What of New York City, an internatioinal city (even in the 19th century?). I think not fighting in 1861 would lead to numerous battles in the future, and a fractured, if not failed United States.
Although the Civil War was extremely tragic, it allowed us to address the issues we fought over head on. It settled the great question of states rights, which had consumed the nation for the first half of the 19th century.
There is this place called academia where they discuss stuff like this.
Which is why it had to be fought. We're perilously close to the same situation today; the cartoon showing the United States split into bi-coastal enclaves of blue states with the broad red middle and south renamed "Jesusland" is funny but also has serious overtones. We're not out of the woods by a long shot.
What would trade policy look like if the South had been allowed to secede? Probably it would have developed along the lines of our trade relationships with other Third World "developing nations," which is what the CSA would have become. The southern aristocracy was not really concerned with political power; their major concern was with propagation of their position as aristocrats, which was threatened by the abolition of slavery. The writing was on the wall by 1860 and none of them wanted to go through the transformation to having to compete in a free labor market. Absent the compulsion of Northern rule, they would have continued their slavery-based agricultural economy for as long as they could. With the full arrival of the Industrial Revolution (and more importantly the proliferation of cheap firearms that ensued), they would probably have eventually been overthrown in a bloody slave/abolitionist revolution. But the further you try to project what "might have happened," the further you go down the road of Science Fiction. In fact there was a series of SF books written a few years ago based on that very premise.
Also, there is no such thing as a "side-speculation about what might have happened had we not fought the Civil War" that "does not concern itself with slavery and race." Slavery and race affected virtually every aspect of the Southern culture. (It still does.)
"One of the big issues"? It was THE issue. The idea that the Civil War was about slavery is a grade school textbook fiction.
My American Economic History class at George Mason spent a great deal of time on this particular issue. The view of the professor was that by forcing the North to pay the guarding costs of slavery via the Fugitive Slave Law, the South was able to perpetuate slavery despite the fact that it was actually a very expensive system to maintain. Had the US Congress simply repealed that law prior to, or upon the sucession of the Southern states, then the South couldn't have afforded to continue holding slaves, except for in some pockets in the deep New South. The Underground Railroad and inability to recapture escaped slaves would have effectively ended slavery with minimal bloodshed.
I don't really agree with that view entirely simply because the issues of slavery and states rights became so deeply partisan over the course of the first half of the 19th century that both sides were too invested to let the other 'get away' with living as they wished. Also, the North, while widely abolitionist, was still sufficiently racist so that the idea of thousands of blacks escaping from the South unchecked was abhorrent.
Tariffs, though an important part of the controversy, were inextricably linked to the slavery issue. I don't think it's possible to look at them as independent factors.
Napoleon realized that whoever held New Orleans would forever be an enemy of the United States, which is why he sold Louisiana in 1803. But even worse than foreign French holding New Orleans would have been the kin-enemy Confederate States owning the outlets for the goods of a truncated United States. It would have been a constant cold war.
Concomitant to a successful secession would have been the Confederate incorporation of Cuba and the West Indies, as well likely as Central America: wherever slavery culture had taken hold. This would have kept slavery alive for quite a long time, several generations.
Imagine that the South persisted into the 20th Century. After taking over Cuba and Mexico, which would have given it everything from Texas to California, while the North satisfied itself with the Pacific Northwest.
Then comes WWI and Germany makes an alliance with the South and the North joins the Allies.
After the French defeat, the South would control the Panama Canal and New Orleans. Moreover, with a partner in Germany, the South would gain access to the technology it might have lacked.
By virtue of the Axis victory, much of Africa would remain in the hands of colonialists even more committed to slavery and apartheid. One might also expect a very different map of Palestine.
After that, it gets a little hazy.