“You still spouting that crap? You know damn well it isn’t even close to being true.”
It is mostly crap. The South was becoming an economic backwater compared to the North. They were falling behind in population and representation in Congress. The only way to keep up was creating more slave states to maintain some parity in the Senate. That was what States Rights were about. Expanding slavery into the territories. It was now or never for them.
Allow me to educate you. You have clearly learned a lot of incorrect information.
The South was an economic powerhouse. It produced 72% of the Nation's federal revenue, even though it had 1/4th the population of the North. The South would have been far wealthier if it hadn't been required to send money to the North.
It's lack of representation in congress is why it was taxed so heavily compared to the North, and it is why it finally realized it would never get a fair shake economically because the Northern coalition controlled congress, and they liked the fact the South was paying most of the bills.
As far as "expansion" of slavery, that was impossible. There was no place that slavery could expand into. All lands suitable for plantation farming were already cultivated, and all western lands were at that time, unsuitable for farming.
We can only grow cotton in West Texas, New Mexico, Arizona and California due to modern irrigation systems that didn't exist back then, and wouldn't exist for another 50 years.
So the claim that slavery would "expand" was just a lie.