IMO, you missed the mark as (coming from someone that grew up in the "occupied land") the American Civil War was an economic clash (first and foremost) that used slavery as a focal point, after the fact since President Lincoln's first motive was to "preserve the Union". Why? The north actually needed the south's wealth as it dwarfed the rest of the country (1861) making the CSA as the fifth wealthiest country on the planet.
A political solution was not in the cards, per the radical republicans as a military conquest would not only quell the south's political power (how many POTUS, pre-1861 were from the south?) but allow them to extraappropriate much, if not all of the wealth from below the M/D line. That's what "reconstruction" was really all about, a kleptocratic feeding frenzy.
Now that you understand this was a forcible entry situation with the end game of "wealth redistribution" perhaps you will have a better understanding of the underlying animosity that exists to this very day.
Botton line is simply this...since 04/1861, the USA is a country held together...by strict military force, period.
There may be hope as it has only taken ~800 years for the Irish and English to begin a reconcillation.