In both instances, supposedly "sovereign" regimes announced themselves (Saddam when he seized power in Iraq, and Southerners when they formed the Confederacy). They kept themselves in power in part by popular will (the Sunnis in Iraq and the whites in the Confederacy), but there was also a large and violently oppressed population (the Shia and Kurds in Iraq and blacks in the Confederacy).
A "foreign" sovereign (the United States in both instances). . . went to war with the rogue state. There were, of course, many civilian casualties, not to mention all the other gruesome outcroppings of war. The foreign government won, but the victory was not clear-cut. Indeed, a violent and armed resistance representing the old order continued for years, targeting those who wanted a better day (those persons consisting of the democratic forces in Iraq and the blacks and sympathetic whites in the defeated Confederacy). The KKK continued its insurgency, consisting principally of terror and murder, for years. The Saddam dead-enders will try to do the same in Iraq.