In a alternate 1944 caused by the Temporal Cold War, the Wehrmacht was able to conquer Europe and the United States. Their occupation was fiercely fought against by the American Resistance. This timeline was later averted by the crew of the Enterprise from 2155.
In a alternate timeline caused by Leonard McCoy saving Edith Keeler, the Wehrmacht took advantage of the neutrality of the United States of America and developed atomic bombs and V-2 rockets. Using the rockets to carry the bombs, Germany succeeded in taking over Earth, therefore erasing the United Federation of Planets from history. This timeline was later averted by James T. Kirk and Spock.