Where to begin?
No, it was not against the Constitution to succeed from the US pre the War of Northern Aggression. Long prior to South Carolina, Massachusetts threaten to do so.
Until the battle of Antietam / Sharpsburg, it was Lincoln's War to preserve the Union [illegally]. Afterward, the Yankee battle plan never surviving first contact with the Confederates, Lincoln revived Great Britain's King George's American Revolutionary War plan to free the slaves upon service to the Crown in the form of the EP so dependent was the Yankee army upon "citizenship upon service" of immigrants who [oh yeah] came to America to free the slaves.
England offered manufactured goods cheaper than Southerners could buy [tax] from the north. Basically, the northern cotton shippers had no cotton to ship from the South. It was Southern cotton that bought the British Enfield and the CSS Alabama.
But did the South depend too heavily on King Cotton? Yep. We were a monoculture at the time. To a lesser degree, not too long ago it was tobacco. Today, we harbor manufacturers and multi-agri-business.
Today, the slaves are Democrat party-liners. Joe Biden threatened to "put y'all back in chains."
Remember?