Hey, slick, let's look at what they said in those declarations of secession at the state level.
www.jacksonfreepress.com
Mississippi's Declaration of Secession: "Our position is thoroughly identified with the institution of slavery - the greatest material interest of the world. Its labor supplies the product, which constitutes by far the largest and most important portions of commerce of the earth. These products are peculiar to the climate verging on the tropical regions, and by an imperious law of nature, none but the black race can bear exposure to the tropical sun. These products have become necessities of the world, and a blow at slavery is a blow at commerce and civilization."
From Texas' Declaration: "In all the non-slave-holding States, in violation of that good faith and comity which should exist between entirely distinct nations, the people have formed themselves into a great sectional party, now strong enough in numbers to control the affairs of each of those States, based upon an unnatural feeling of hostility to these Southern States and their beneficent and patriarchal system of African slavery, proclaiming the debasing doctrine of equality of all men, irrespective of race or color-- a doctrine at war with nature, in opposition to the experience of mankind, and in violation of the plainest revelations of Divine Law. They demand the abolition of negro slavery throughout the confederacy, the recognition of political equality between the white and negro races, and avow their determination to press on their crusade against us, so long as a negro slave remains in these States."
Sorry, man, the Civil War was about slavery.
Actually, there were a lot of threats to slavery, mostly in the form of all that new territory in the west entering the Union as Free states and voting to change the constitution to end it. No slave states had been admitted to the union since 1845, and the Kansas-Nebraska Act pretty much meant all the new states would be free states.