While interesting, those flags are incorrect. The Cross of Saint Andrew based Confederate battle flag never flew over the Confederate capital because it's not the Confederate national flag.
That flag changed over the course of the war, but the last one was this:
Further, since the Confederacy would likely have not had world conquest aqspirations, those sprang from the New England Puritan culture, the same one that brought slavery to North America in the first place, it's unlikely that the Confederate States would have condoned a war with Spain, against Germany, or other subsequent foreign meddling. Without substantial US participation in World War One, Hitler would have been just another street bum in Vienna or Nuremberg. The space program photo is a non sequitur.
EDIT: If you want an entertaining alternative history novel,
Guns of the South by Harry Turtledove is a pretty good one, far fetched, but interesting. The same author wrote
How Few Remain a second alternative history about a second War Between the States.