Quite easy, a president other than FDR. America wasn't all that different than Nazi Germany and with a slight change in American Presidents, such as Lindbergh, Kennedy's Father, or Ford and you would have America quite supportive of Hitler's anti-semitic policies and eugenics program. Hell it wasn't until the 1970s that that the U.S. stopped forced sterilizations of children who the Government felt should not reproduce. There is a lot more dirty laundry as well, far too numerous to list.