He did. He wrote a series of books that ended with the end of World War II. In this series, the South freed the slaves in the late 19th century, but African Americans were still second-class citizens who couldn't vote.
When WWI came around the South sided with the Allies, having close ties to England and Franc, and the North sided with the Central Powers. Neither side sent troops to Europe, and instead fought a long bloody trench war in North America. During the war, African Americans in the South rose up in a socialist revolution. The were eventually crushed, but this hurt the Confederate war effort. The North fought a two-front war, holding the South at bay while they invaded Canada and successfully wrested it from British control.
Eventually, the Central Powers won the war, and the Allied nations were forced to pay heavy reparations to the victors. This weakened the already strained Confederate economy and caused drastic inflation. By the time the stock market crash of 1929 came around, the South was in really bad shape. From this chaos, the fascist Nazi-analogous Freedom party rose to power, and similar fascist regimes took control of France and England. The Confederates started locking away African Americans in concentration camps and eventually started murdering them.
Tensions increased between the two nations, and, eventually, the South invaded the North. The US fought a losing battle for a while but was able to turn the tide and utterly defeat the South, but not before both sides set off atomic bombs. The series ends with the North completely subjugating the South post-WWII.