One way, perhaps the only way, to un-divide a nation is a civil war and then wait five generations. From 1861 to 1865, 620,000 Americans died before democrats tolerated the idea that they could not have slaves. I wonder how many deaths and generations it will take the next time around before they are willing to tolerate their lack of slaves again.
That was a war of southern Independence and most fought for states rights and to free themselves from Federal tyranny. Plus thought of killing Yankees by the gross is to alluring to pass up.