The Civil War was a pretty serious one and it must be noted before the Civil War itself, the South threatened to secede twice, once during the Jackson administration and again during the Taylor administration, both times Henry Clay produced compromise that staved off the conflict, in the latter case President Taylor who didn't want to appease the South(ironically the largest slave holder we ever had as President was the most unwilling to accommodate the South including Lincoln) died and was replaced by someone who did. In 1856 just like in 1860 the South promised to secede if the Republican were to win the election. While the threat didn't work in 1860(in part due to them sabotoging the Democrats chances by splitting), it did in 1856. So the threat of southern rebellion had been a long standing one.Or rather serious uprisings, not including the civil war...
Why is it when South American countries or African countries gain independence, their countries go through a vicious cycle of coups, civil wars, dictatorships, corrupt governments etc. but America has somehow been able to avoid these, again excluding the civil war?
During the war of 1812 there were murmurings in New England of rebelling as well. Finally in the very early days of the US there were minor rebellions like Whiskey and Shay's mentioned. All three of these were over policy.
Another point is the US gives a great deal of autonomy to it's states, for unconstitutional state action to be overturned it is actually required someone sues over it first(hence why so many clearly illegal ridiculous city and state laws remain on the books across the country in various places) and even here deference is given to legitimate state interests. Even the south who did rebel in the name of "states rights" wasn't having their way of life attacked so much as shoving it in everyone's face. It's a pretty good deal, even more so today, you get federal grants, unbeatable military protection and your citizens can come and go within the states as they please.