This topic may have come up before, but I'd like to hear people speculate on the following WI:
Let's pretend...during the lead up to the 1860's, the legal standing of slavery in the United States becomes more entrenched as a result of a number of supreme court decisions. It is the law of the land, there seems to be no likely change, and it may expand into the western territories. In addition, other factors (tariff law, etc) trend in a way that does not favor the industrializing north. In 1860, number of northern states, including most of New England and several great lakes states, seek to secede from the United States and form the "North American Union". For the sake of argument, lets presume that the NAU at secession includes all of New England, New York, New Jersey, Pennsylvania, Ohio, and Indiana, with substantial pro-secessionist sentiment in Michigan, parts of Illinois, and in scattered locations in Plains and western territories such as Colorado.
Questions:
How would this happen? (feel free to revise the original premises as needed if this helps - I just want a flip-flopped ACW)
Would a United States comprised largely of slave states, slave-holding border states (like Maryland, Missouri, Kentucky, etc) fight to hold the union together or just say good riddance?
If it came to war, how might the military campaigns develop and where would they be waged.
How would other nations react - if there was a civil war would they be more or less likely to recognize the NAU than they were the CSA.
Who would win and why?