The war of Southern independence was for a separate nation, not control of the North.
If the Confederacy had won, the Federal government would have made decisions for states remaining in the Union. Southern leaders wouldn't have had a say in government of Northern states.
It's just speculation, but slavery would've eventually been abolished, certainly long before now. In any case, the actual condition of black people in the U.S. was little better from 1865 until 1965.