[Modernman]

And, may I say, thank God for that. However much I dislike what has become of the federal government and federalism, a world in which the South won the Civil War would be a much worse one all the way around.

If the CSA had managed to achieve independence, it is a certainty that the two countries would have fought subsequent wars.

[Protagoras]

If the CSA had managed to achieve independence, it is a certainty speculation that the two countries would have fought subsequent wars.

Edited

[The Iguana]

If the CSA had managed to achieve independence, it is a certainty that the two countries would have fought subsequent wars.

It seems to me that there would have been a high probability of that as well.

Assuming that the rump of the union had stayed together. Further secessions (such as by the Far West, or by the Mormons) - and further wars - might have followed.

Along with alliances with European Powers.