Some further thoughts:
In regards to the issue of race relations, I am not sure where this idea that the Civil War and Reconstruction are responsible for the violent nature of race relations in America. As noted previously, anyone examining the history of slave revolts, their violent suppression and the discourse surrounding “uncontrolled blacks” — which is to say the larger racial ideology — can find ample evidence that dehumanization of blacks and fear verging on loathing were already features of a violent system. Neither the Civil War nor Reconstruction created this, and I think it naive to think they even had much influence one way or the other.
In regards to a post-Civil War development of the Confederate States, it strikes me that far too many posters are assuming away a legion of difficulties to arrive at a present only slightly different than our actual present. Of course assumptions are inevitable, but one should start with some rigorous examination of the post-War possibilities.
Most obviously there is the instance of United States - Confederate States relations. They are unlikely to develop chummily. The issue of slavery would continue to irritate:
First, the Abolitionist movement in the North is unlikely to disappear, and depending on the scenarios for the end of the War, might remain politically strong.
Second, the issue of escaped slaves fleeing North and West, already a problem for the South prior to the War is likely to continue and grow worse, above all if we presume the Abolitionists remained strong in the Union. Certainly, the incentives to compromise or respect Southern “property rights” over human beings are largely removed. Slave flight to the Union territories would present not only serious political issues, it would represent a real loss of capital for the South. We may presume a militarized border in the developed East as Southern states attempted to suppress flight with “bleeding Kansas” style guerrilla conflict in the West.
Again, depending on the scenario, the Union is likely to have the military strength to close off western expansion, which will prove problematic for the South. Increased militarization of both states will prove to be a drain, but more so on the South. With economic developments largely running against it, all other things being equal, its long term future as a healthy state looks doubtful. As a corollary, one might suppose — although this is not necessary — that development of the West might move faster as the more powerful Union pushes to lock in those territories and their presumed resources as quickly as possible.
Third, a more militarized North America introduces a very different developmental dynamic, with less surplus being devoted to productive capital investment and more to unproductive — in absolute economic terms — security investments. Continued tensions along the border are likely to fuel conflict, if not open war eventually. One might not be able to rule out Northern support, direct/official or indirect/unofficial for slave revolts with corresponding cycles of violence undermining internal investment in the South. Effects on the North seem less clear than on the South which quite clearly begins in a position of weakness which is unlikely to improve except under the most optimistic assumptions. However, in re the ideological make up of the North, I think it unwise to think in terms of “liberal North” and thinking of the modern North East. For example historically as much progressive — using the term in its historical usage — derived from the Mid West. I don’t believe there is any reason to suppose a Communist influence or success in the North, as a poster in the other thread did. Indigenous American socialism was never Communist and seems to have petered out on its own account without real reference to the South, but I advance this with caution.
Finally in re the question of subsequent secession, especially in the South, I think MEBruckner rightly hit upon the core of the question: once the door is opened to using separation as a means of solving political conflict within a political entity, it becomes easier to do so in the future. The Union is likely to adopt strict measures to suppress this, leading to greater federalization, but this is not a necessary response. His scenario of Northern balkanization under outside influence is also possible and the tensions not to be underestimated. In the South, however, their very political logic will tend towards fragmentation which if not leading to break up of the Confederation (outside pressure may be enough to prevent this) will certainly undermine the effectiveness of the Confederate state and likely lead to quasi-balkanization.