So let’s just say that some of the main scientists for the Manhattan Project die in a plane or car crash. Operation Downfall is launched, US casualties are over two times what they were IOTL, comfortably placing it above the American Civil War as the bloodiest war the US has ever fought. Truman is even more unpopular than IOTL and gets beaten by Dewey or Taft and NATO never comes to be, the Marshall Plan is neutered and Eisenhower decides to not run for President. The US is only loosely tied to a ruined Europe and the occupation of Japan ends after four or five years. What is the global effects? Especially in relation to the Cold War.