The South certainly couldn't have won the Civil War in the sense of invading and subduing the North. I think odds are good they could have "won" a political victory, in the sense of dragging the conflict out with superior generalship (which they had) until people in the North got tired enough of it and the North simply gave up and recognized the Confederacy, which was all they really wanted in the first place.
It's one thing to concede defeat and peacefully coexist with a tiny country in southeast Asia. That's not a hard sell, politically. A country that represents half of your former territory, borders your capital and has a very long border with you, and has a history of warfare against you is not so easy.
