While many people think of the Civil War as a war over the issue of slavery, the truth is that it was much more complex than that. Slavery was a major issue, of course, but the causes of the Civil War were brewing for a long time, dating all the way back to the inception of the United States. From the outset, as the Constitution was being written, there were deep divisions among many people about how the balance of power between the states and the federal government should be determined and structured. Many in the Southern states were in favor of a less-involved federal government, while the Northern states supported a unfied nation with a more powerful central government. So slavery was just one of many issues that divided the nation, as the economic backbone of the South was dependent on slave labor, and giving it up would mean giving in to the federal government and also losing out economically. The Civil War was, in many ways, a test of the strength of the federal government over the individual states, and in the end the federal government won out.
This had major repercussions, and the federal government grew more powerful after the war. The strength and scope of the federal government continued to grow, to the point where there is no question today that the federal government is more powerful than the individual states. Yet this powerful federal government continues to be problematic for many people, and the deep divisions that sparked the Civil War continue to exist. While it seems unlikely that the states would ever wage war on each other again, it is true that some people in some parts of the nation would still like to see the South (or some Southern states) secede from the Union.