Correction. We never "deposed the Japanese emperor. Despite the fact that he was depicted him as on a par with Hitler during the war, Truman sensibly overruled his New Deal advisors who demanded unconditional surrender and accepted the Japanese condition that Hirohito be kept on his throne.
As to democracy, as Ohioan points out Germany (unlike Iraq) had recent experience with this system in the Weimar Republic. Japan did too though to a much more limited extent in the 1920s. Interestingly, we let the Japanese vote in all-Japan elections in 1946 (less than a year after Hiroshima) under their pre-war constitution!!!
Yes, the emperor was kept on the throne, but the new Constitution stripped him of all political power.
As to democracy, as Ohioan points out Germany (unlike Iraq) had recent experience with this system in the Weimar Republic. Japan did too though to a much more limited extent in the 1920s. Interestingly, we let the Japanese vote in all-Japan elections in 1946 (less than a year after Hiroshima) under their pre-war constitution!!!
As for experience that Germany and Japan had had with Democracy, it had been bad experiences, resulting in unstable governments and the rise of thugs to power.
The U.S. gave stability to both nations (McCarthur essentially writing the 1946 Japanese Constitution) and thus both nations embraced the concept that the ballot was better than the bullet in resolving differences.