The answer I expected, but really an example of historical myth making. Neither Germany nor Japan ever represented a threat to America's borders or way of life either before or during the war. Japans expansion into Southeast Asia had to do with their desire to become a major power, but lacking the resources to do it. They would have been happy to avoid the U.S all together, but felt threatened b . Once the war started it was a forgone conclusion that they would lose. Their industrial base simply could not keep up with ours.
Germany had no interest or intentions toward the US. Hitler was much more interested in the land and resources to the east in the Soviet Union. He had already failed to conqueror Britain and if we had simply let him and the Soviets slug it out for years it would have eliminated both as threats. We could have covertly supported resistance in Western Europe to weaken his hold there at the same time. Germany would never have had the resources or range to affect America on the other side of the world that much. It also must be said that Germany's racial attitudes were not much different than many American attitudes only a few generations earlier. Hitler was a fervid anti-communist, but he had little reason to despise America.
World War 2 really should be seen as the war that made the world safe for communism. There is very little difference between a world with imperial, fascist powers like Germany and Japan around, or totalitarian communist powers like Russia and China around. In fact if Japan had not been defeated Mao would have died a forgotten student revolutionary and tens of millions of Chinese would not have had to die in the Great Leap Forward.