Abraham Lincoln invaded the South to “preserve the union” (akin to “preserving Yugoslavia” - the one created by the same Allies that demanded it be dismantled seventy years later). Many more than 8,000 people died in his illegal war to stifle the states’ guaranteed constitutional right to leave the union.
Don’t let the facts cloud your biases, though; the Southern states (birthplace of so many founding fathers) were every bit as “American” as (if not more than) the Northern states (and still are).
By the way, states have no rights. States are governments, and governments have no rights. They have powers. Only people have rights. No state has any imagined "right" let alone any power to violate federal law. The Constitution is quite explicitly clear on that point.