That is what MacKinlay Kantor thought and wrote about in his book published a century after the war. But it a silly and sentimental notion.
How many independent nations willingly give up their independence?
Usually national elites, institutions, and sentiments grow up that give new nations an interest in independence.
Rivalries that arise between nations, especially after bloody wars, may weaken over time, but not to the point that they surrender their sovereignty.
I think this is a good prediction, though I think the USA would have melted into the CSA.
Some troll or other will always say something absurd like that, thinking that it will make him interesting to people.
Based on the premise that the South maintained it's independence and established trade with Europe, much of the European trade with New York would have been diverted to Southern ports. If the North kept it's high tariffs (which I doubt it would continue to do) much Southern economic traffic would have been carried by the Mississippi, and other trade would been carried overland.
The Border States, upon seeing that the South was gaining prosperity from European Trade, and after having been reassured that the principle of secession was established and accepted, would leave the Union and join the Confederacy. It would become a preference cascade in favor of the South.
You think it's nonsense because you dismiss out of hand anything that goes against what you wish to believe, but if you are being honest, you would have to admit that the border states would have eventually joined the South, if the South was creating the economic activity that was enriching them. (And if there was no risk for them to do so.)