However, the issue of states' rights predates that of slavery by several decades. As early as the Whiskey Rebellion in Pennsylvania, the Alien and Sedition Acts of the late 18th century, and Tariff of Abominations in the 1820's, the collision between Federalists and Anti-federalists pointed out an ideological schism that would finally sunder the nation. That it was made manifest in the issue of slavery doesn't mean that that issue DEFINED it. The immediate cause of the War was secession, prompted by abolition, rooted in the notion of Federalism. Attempts to wed the competing notions of federalism and state sovereignty had failed, and the course of war was cast.
Thank you for an enlightening discussion, and for giving me cause to dust off some forlorn but beloved reference materials.
The most immediate cause of secession was the election of Abraham Lincoln on a platform that Southerners expected to be an engine for ruining the South economically, and permanently changing the relationship of the federal government to the States, in order to cement and entrench Lincoln's factional victory.
Southerners feared that Lincoln, in possession of the federal government, would use the Supremacy Clause to abrogate the Ninth and Tenth Amendments, and the rights of the States. Which is about what has happened.
If you look at Non-Sequitur's long post of quotations from Southern secession speeches to you, you will see those concerns reflected there, as much as, or even more than, any solicitude for slavery per se, or even its economic ramifications.
Remember that Marxists are determinists, and economic determinists in particular. That is one reason that pushing the line that "it was about slavery and nothing else" comes so easily to them. It is convenient to their political purpose of building a Marxist superstate, and consonant with their own indoctrination by senior Marxists.