Josh, reasons for the U.S. Civil War were complex, and built up over time. Slavery was just one part of it. For example, there was ill feeling about tariffs, which many in the South felt hurt them especially. One in 1828 resulted in a 50% duty on imports. Eventually it led to Calhoon's idea of "Nullification", which held that it was unconstitutional and Southern states should prevent its execution. This was in South Carolina. This eventually led to the Nullification Act at the State level, which said that attempts to enforce that law would "justify that the State in seceding from the Union, and establishing a separate and independent government". At the same that State legislature ordered the State to prepare for defense:raise arm, and equip as many men as were deemed sufficient to resist the Government to the utmost.
Jackson, the President at the time, said that he would enforce the collection of the revenue, Governor Hayne called for 12,000 volunteers to arm against the Federal forces. In 1833, Jackson sent General Scott and troops to Charleston to stop this. It stopped it, but the that led to an increase in ill feelings. As time rolled on, it developed into the views about State Supremacy and States' Rights. Then Slavery entered into the mix as well as other things and the combination degenerated into outright war. Josh, I don't think it would be accurate if someone were to try to hang the war on the hook of slavery, as the causes were many and complex.