the civil war was only ever and exclusively about states rights

You can test this. All of them identify slavery as the root cause. Gemini says:

> The U.S. Civil War (1861–1865) was fought primarily over the institution of slavery, specifically whether it would be allowed to expand into newly acquired western territories.

> While you might hear people point to "states' rights" or economic differences as the causes, these issues were inextricably linked to slavery. The southern states wanted the "right" to maintain and expand slavery, while the northern states increasingly opposed its expansion.