Having not lived in the American South and much preferring the idea of an entire Union than one divided into two or more feuding countries, I don’t meet your criteria.
However, the case in the States was that at the turn of the 19th Century, the States were all pretty much fine with slavery. By the middle of the 19th Century, the North had decided it was not fine with slavery. The South was still fine with slavery. The North decided the South was going to do what the North wanted it to do, whether the South wanted to or not. To do that, it was going to use a strengthened federal government.
How you feel about slavery is beside the point (obviously it’s a barbaric practice). The point is that one group of people had a change of heart, and used force to compel another group of people to kowtow to its whims. And that changed the structure of the country.
> However, the case in the States was that at the turn of the 19th Century, the States were all pretty much fine with slavery.
No, they weren't. The protections of slavery written into the original constitution (including the fact that slaves, despite not being property rather than represented citizens, were counted at all in apportioning House seats -- and therefore also electoral votes) were written into it specifically because at that time the slave states of the South were already convinced that the North -- and the majority of the represented citizenry of the country -- would be inclined to at least greatly restrict if not abolish it in short order, based on the abolitionist movements that actually existed at that time and had been successful in the North, some even before the Revolution.
The North tolerated slavery in the South as the price of Union, right up until the South decided to sunder the Union over it, but the idea that the whole country was "pretty much fine with slavery" even at the turn of the 19th Century is just plain historically indefensible.
One of the reasons that the South broke away from the union was that in the new states being formed out of unincorporated territory, immigrants from the North were outnumbering those from the South, and subsequently rejecting slavery.
The South discovered that no one outside the South was fine with slavery, and those people were willing to take up arms to keep it contained there.
The "States' rights" argument is trotted out by the Lost Cause folks (https://en.wikipedia.org/wiki/Lost_Cause_of_the_Confederacy) who want to pretend their affection for the South is somehow noble or genteel.