These diagrams from the March 2, 1942 issue of Life detailed the Nazi invasion of America shortly after the attack on Pearl Harbor. Check out such alternate reality battles like the bombing of Detroit and invasion of Norfolk, Virginia.
These maps were created as a follow-up to an article about an American defeat in WWII by pioneering science fiction author Philip Wylie, who wrote the proto-superhero novel Gladiator. These maps were made in the early days of US involvement in World War II, so there was a sense that this invasion was a real possibility. You can read more about these maps at Ptak Science Books.