I think Southern Victory is a screw for the United States. Sure, it wins out in the end, but to get to the end of the series, it has to go through not one, not two, but four wars against the Confederate States. According to the Great War series, the United States loses a excess of 1.5 million soldiers killed in action in the Great War alone. The United States is scarred from seventy years of continuous warfare, not just physically, but psychologically. The American people in this timeline have had continuous tastes of what it's like to see blood and carnage in the same way the Europeans did in the 19th-20th Centuries. War cemeteries must be huge in this timeline's USA.
Then there's the Population Reduction by the Confederacy, so the US is going to have to deal with the legacy of a 20th Century industrialized genocide occurring on their continent in which eight million blacks were gassed or shot, according to In at the Death. American children will probably have excursions to Camp Determination like how in Poland OTL, they have excursions to Auschwitz.