The earliest POD for a earlier American Civil War can be found in the 1832 Nullification Crisis in which tensions between North and South over the tariffs of 1828 and 1832, which Southerners called the Tariffs of Abominations, reached a breaking point when South Carolina threatened to secede from the Union over it, even preparing to raise a military to resist federal enforcement of the tariffs in February 1833, followed up by Congress giving President Jackson the right to use military force against South Carolina in the Force Act in March 1933. On the same day, however, Congress passed the Tariff of 1833, which South Carolina accepted, ending the crisis.
South Carolina's attempt to raise a military indicated how far it was willing to go to protect it's 'state's rights' and the 'Tariffs of Abomination' were detested by a majority of the South, not just South Carolina. It's feasible to imagine that had South Carolina chosen to reject Congress's proposed Tariff of 1833, it could've just been the first state to leave the Union, as it was in OTL's 1860.
With that in mind, what would've been the differences between a 1833 American Civil War and our timeline's American Civil War in terms of progression, technology, etc?