They didn’t defend their own turf initially or exclusively. Rather they attacked US Army soldiers at Ft. Sumter, which was built by the US on a shoal, said shoal never being part of the land mass of South Carolina.
Further, they attacked US forces in the territories of what is now New Mexico, and Arizona.
They also attacked NY City, and Vermont as well as the better publicized attacks in PA, MA, KY and MO
States' Rights was abused THEN as now; Instead of being considered equal countrymen, the South was pushed around while its economy was undermined by the same Bluebloods, Industrialists, and Intl. Financiers who've now helped crater this entire nation.