Re: Unnatural Union.
I don't believe we will ever know that. These two factions were not at peace with each other and had come to alarming odds several times, and slavery had very little to do with it. The War of 1812 showed New England's preference to not support the War and attempted to rejoin Great Britain. The addition of territories caused calls for secession by certain states. An attempted power grab by the Federal government in 1790s caused several states to declare and remind the central government that they would retake their delegated powers. The fight over free trade and the placement of trans-continental railroad were powerful divisive issues. Prior to the Civil War, the threat of secession, was a known tool to settle issues if compromise did not work. The possibility of secession over any issue, at anytime was real.
An American South, without slavery, did not mean the end of political issues that could break up the Union.