Sectionalism and "state's rights" are certainly major issues, and you have in past posts brought up the issue of economics and tariffs. Stephen A. douglas's concept of "popular sovereignty" in the territories also caused a great deal of soutehrn consternation.
The big issue, if you had to name just one, would have been "state's rights." This problem cropped up constantly from the 1820's to the 1860's. (In a sense, it is still an issue today - but dealing with other matters). "State's rights" was a code word for nullification and the continuation of slavery. It had less to do with the States' relationship with the Federal government, than it did with the political balance of power. The southern stats could do the arithmatic. The old North's population was growing faster than that of the old South. The new West and Plains states and territories were predominantly free territory. The balance of power on the abolition-related issues had already passed away from the South in the House. However, the Southern Senators, with the help if border-state and sympathetic Northern Senators had been able to hold the line on legislation the the South felt threatening. Thus, legilation such as the Compromise of 1850 and the Kansas-nebraska Act of 1854, could only move forward with Southern participation. And, the South had a majority in the US Supreme court (as in the Dred Scott decision).
When the South felt politically marginalized, the issue of "State's right" came again to the forefront. When that wedge issue lost its effectiveness, the South chose the course of secession.
SOME of what you posted MAY be true, but the majority is NOT. the portion that MAY be true is a part of the lust for LIBERTY for southerners.
free dixie,sw