At the beginning of Ken Burns’ CIVIL WAR documentary-miniseries, Memphis based historian Shelby Foote comments that before the Civil War government documents usually referred to the USA as a plural. “The United States of America are resolved that…”. After the Civil War it became singular: “The United States of America is resolved that…”. Essentially (this is oversimplification) the early USA was a collection of 13 semi-autonomous small countries (which is certainly how Britain dealt with them politically- they were seen as different colonies that happened to be on the same continent). It was hardly a unanimous decision that they remain this way- some wanted an extremely powerful central government, others saw little use in a central government at all, but ultimately after screaming and drama and political intrique and death threats and walkouts there was compromise and the Constitution’s drafters did their best to create a strong central government that allowed states to still have strong independent governments. However, 70 years later the states really did not see themselves as a united country.
In the late 1850s states still issued their own currency (Federal standardized currency was also around but it was pretty much a bust) and the battle about who should win in Federal v. State arguments was still hotly debated. There had been numerous moves to dissolve or for one state or another to secede from the union of states and it didn’t always come from South Carolina (though they pretty much wanted to secede if they felt Bostonians were breathing in too much and using up too much air) or from the south- Vermont, New Jersey, and New Hampshire all talked about secession at one point or another, probably others, but it never went past talk. It was not until the very real economic threats of the 1850s that the southern states wanted to not only pull out but form their own separate nation.
The north was [mostly] industrial and small farms while the south was, of course, agricultural with plantations or “super farms” and only limited industry, though both north and south had excellent ports and shipping infrastructure. The economies were so diverse that it was impossible to make trade treaties with other nations that benefitted the south without harming the north and vice versa. Then there was the slavery issue which is too huge to go into.
When they seceded from the union the southern states didn’t see themselves going against the whole point of the American Revolution but in replicating it. “Our great-grandfathers reached a point where they could not keep their way of life and reach their greatest prosperity and happiness as part of the British Empire, so they seceded and formed a country where they could go their own way; we’ve reached the same stage with the United States, so we’re pulling out and forming a country so we can go our own way.” And it’s not completely illogical, plus many of these people would have grown up on the stories and lionization of the revolutionaries (and as a reminder of how close in time it was, Robert E. Lee’s wife was the adopted granddaughter of George Washington [her father was Martha Washington’s grandson and George adopted him when he was orphaned]).