I have read the series up through the end of WW1, and just bought Blood and Iron 3 days ago. Personally, I think Turtledove could cut the number of pages in every book of the series by 30% if he stopped repeating himself every 5th chapter. But the series is intriguing so I'll continue to plod along
Would it have been possible for the army of Northern Virginia to inflict a crushing defeat on the army of the Potomic and then march to Philadelphia? What would Lee accomplish if he did, 200 miles from friendly territory with only 70,000 men? I doubt such a move would have brought English and French recognition, which would have been the only way for the CSA to win independence.
If the CSA had won though, I believe Turtledove's vision of the slow abolition of slavery in the south would have occurred. I can believe that socialism would be a big force in both halves of the country.
I doubt the USA would tolerate the kind of military incompetence that could lose the Civil War for long. The means would have been put in place to guarantee victory if given the chance (excuse) to wage a Second Civil War. "Never again" is a powerful motivator.
If a scenario were made featuring the USA vs the CSA, I think the CSA should be required to remain communist, to simulate the effects of slavery. The USA would be republic as opposed to democratic, to simulate the influence that state governments had on the Union war effort. The CSA would probably be militaristic, to reflect their better performance during the early years. The USA would be industrious. Both sides were highly innovative, maybe scientific for each?