A Confederate victory would be interesting for the Anglosphere concept, namely that societies that speak English are predestined to be democratic, free, equal societies. The CSA in practice would have collapsed into military rule in the medium term and its long term future is likely to be two generations, the USA would want it back as much as South Korea wants North Korea back but would intervene if for no other reason than to keep anyone else from so doing.
The failures of the Confederacy, as in the cases of the USSR and Rhodesia are built into the system. 2/3 of a state's population holding the other 1/3 as slaves is a foundation that guarantees no democracy will endure in any such system. The Confederacy had no financial infrastructure worthy of the term, and it functioned best in the real war when run by the generals, who in even the most plausible short-victory scenarios will have experience of their own, and if the CSA ekes out a political "win" in 1865 then half the CSA will have been run by military dictatorship for quite some time. The Confederacy cannot simply abandon slavery, nor will it do so, the Confederacy of OTL only scrapped slavery when Richmond's fall was a foregone conclusion, and any victorious CSA will never do this.
Confederate leaders would do their damndest to keep the rotten structure together but its flaws would be too many circles to square for anyone, no matter how brilliant, co-operative, and long-term-thinking (all words that apply to none of the generals or politicians in the Confederacy) to do so, and the great tragedy of the Civil War is that a victorious CSA would be as much a disaster for the entire South as the defeated one was for black Southerners.