You know the argument that the Civil War was really not about slavery -- slavery was just the spark that set off the war, but each side was really figthing about something else , a commitment to states' rights in the South, a desire to preserve the nation in the North. West Point historian Ty Seidule begs to differ:
Some argue that the South only wanted to protect states’ rights. But this raises an obvious question: the states’ rights to what? Wasn’t it to maintain and spread slavery? Moreover, states’ rights was not an exclusive Southern issue. All the states — North and South — sought to protect their rights — sometimes they petitioned the federal government, sometimes they quarreled with each other. In fact, Mississippians complained that New York had too strong a concept of states’ rights because it would not allow Delta planters to bring their slaves to Manhattan. The South was preoccupied with states’ rights because it was preoccupied first and foremost with retaining slavery.
[. . .]
And it wasn’t just plantation owners who supported slavery. The slave society was embraced by all classes in the South. The rich had multiple motivations for wanting to maintain slavery, but so did the poor, non-slave holding whites. The “peculiar institution” ensured that they did not fall to the bottom rung of the social ladder. That’s why another argument — that the Civil War couldn’t have been about slavery because so few people owned slaves — has little merit.
Of course the result of the Civil War was the beginning of the great expansion of federal power and the diminishing of state power, but that doesn't make federalism the primary cause of the war, unless you consider it in this light: The stronger the government's power is, the more authoritarian it becomes, the closer to totalitarian it gets. What is more totalitarian than slavery, the complete domination of people to the point where they're not even considered human?
Related question: Was John Brown a hero or a villain?