Seems to me these aren't mutually exclusive. I find your argument to be overly concerned with injustice of slavery. No one is defending it. And the southern states absolutely did not want to adhere to the laws set by the northern states.
The civil war was fought because the southern states wanted to maintain their slave economy. It is as clear, cut and dried as that. Individual southerners may have fought for glory, for Suzy to love them, for money, or for any other reason, but the prosecutors of the war effort for the south did it because their economy was dependent on slaves and they wanted that to continue. It's not disingenuous to state that.
If you want to get that reductive than I am right. The Civil war happened because the Confederate States of America fired on Fort Sumter and everything else was ancillary. Just like WW1 happened because the Archduke Franz Ferdinand got assassinated.
Youre argument is overly reductive and your ignorant of history
Florida trying to tell California what to do is by definition not a states rights issue.
In the abstract, they are not.
Its just that the slavery explanation is factually true and the other is false, though it represents part of one sides propaganda (and more strongly that of the retrospective sympathizers of that side than the actual side, which was quite explicit about slavery specifically as the motivation.)
To add to the sibling comments, the southern states hated states' rights when northern states were liberating escaped slaves within their jurisdiction. The Fugitive Slave Act immediately destroys any argument that the Civil War was about states' rights.
As another thread points out, if slavery was prohibited in all the new states from the West, it would be game over in Congress, and the slave states knew it. Hence the Kansas-Nebraska Act.
That said: "save the Union" was a much bigger motivator for Union soldiers than "abolish slavery." That's what made them volunteer.
For the Southern soldiers who mostly did not own any slaves, it was more "defending our homes and our way of life" than "states' rights."
In other words, it's more nuanced than you present.
Mississippi’s is even more explicit https://avalon.law.yale.edu/19th_century/csa_missec.asp - “Our position is thoroughly identified with slavery — the greatest material interest of the world”
The civil war was fought because slave states wanted to force slavery on other parts of our country, outside their own borders.
The "states' rights" framing of the US Civil War skips over which specific right the southerns states were willing to die for. It wasn't abstract, though it was papered over as such.
The history of later southern political leaders (e.g. Richard Russell) confirms that the fundamental issue was the enslavement (ideal, for them) or segregation and oppression of blacks in the US.
Which isn't to say that the state vs. federal power struggle of constitutional interpretation isn't still happening. These cases rise to the SCOTUS regularly. The US Civil War, however, wasn't that.