What would have happened if more southern states tried to secede after South Carolina did so in protest over the Republicans winning in 1860. They tried to get other states to follow their own lead, but none did, not even Texas which had been independent as recently as fifteen years before.
Well, for one, maybe Franklin Pierce doesn't win the election of 1848(and doesn't die in 1850, making Lewis Cass President)? His election no doubt caused a lot of infighting amongst the Democrats, allowing Zachary Taylor to win in 1852, and this is crucially important because it was in Feb. 1856 when the Richmond Massacre occurred, at the hands of radicalized Fire-Eater militias and their Know-Nothing allies, in which 40 Irish immigrants as well as a number of WASP/Scots-Irish white folks suspected of harboring anti-slavery sympathies were brutally murdered.....which inspired several more that year, including the violent lynching of an Italian immigrant couple in Atlanta, and the killing of a Greek store owner and his family in Baton Rouge, La., during that same year.
Had President Taylor not cracked down on the Fire-Eaters, and the people who allied with them, just prior to the start of Buchanan's term, secessionism might have had a lot more success. Only the strengthening of the political moderates in these states prevented this problem from getting far worse, and even then, the Rebels still caused trouble in several of the other Deep South states prior to 1866 when George Fitzhugh was captured(though, arguably, the Christmas Eve, 1864 stabbing death of one of their top bankrollers, Samuel Cartwright, in Jackson, Miss., might have been the straw that broke the camel's back).
OOC: I'm thinking that instead of the C.S.A., we got a lower level insurgency ITTL that, while still supported by a fair chunk of the population, never actually ruled outside of South Carolina. And yes, I did in fact refer to
that George Fitzhugh.