How did the american occupation change japan ?

I believe the answer is: The major cities of Japan were destroyed from bombing raids. Hiroshima and Nagasaki were barren wastelands. Japan had been stripped of its colonial empire

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The bombing of Hiroshima and Nagasaki was the first recorded use of atomic bomb that targeted living human being. After Japan surrender because of the massive casualties, United States began to occupy the nation.

The leaders who were considered to be war criminals from Japan was arrested, japan was required to follow through demilitarization, and Japan was forced to change its government into a constitutional monarchy.