For starters, the south didn't overthrow anyone's government; they opted to leave the Federal union. Secondly, there was no appetite for continuing the war lon

For starters, the south didn't overthrow anyone's government; they opted to leave the Federal union. Secondly, there was no appetite for continuing the war longer than 1865, or for extending Reconstruction much past Grant's term of office. A prolonged occupation of the south, such that white people there could be taught that white-supermacy-is-wrong-m'kay at gunpoint until they finally understood...that doesn't happen in this timeline or any proximate one.