<< Ummm, let's not turn it around. Churchill and Roosevelt were not the aggressors in World War II, nor were they the ones who committed genocide. Maybe some kind of mock trial would be arranged (assuming Hitler could have actually taken the United States, which is complete fantasy), but it wouldn't have been legitimate whereas the Nazis, et al being put on trial was completely justified. >>
Why not? . . . History would have been written very differently if the Allies lost. If Japan had the foresight to INVADE Pearl Harbor, we may well have lost the War.
This topic is a bit moot, anyway. The surviving Nazi high-command WAS tried for war crimes and many were executed (remember the Nuremburg Trials).
Hitler probably would have suffered the same fate as Italy's leader - killed by his own former followers - if he had not (probably) committed suicide. If - somehow he had survived - he would have had the same fate as the other War criminals - Execution.