What is one way that Japan changed following world war 2?

Japan established new constitution after World War II.

Explanation:

The SCAP (Supreme Commander for Allied Powers) was the military leadership over Japan after World War II which prioritized the amendment of the Meiji Constitution when the Japanese had a hard time carrying out the task.

The government of MacArthur who was an American US general of SCAP volunteered to write the draft for the Japanese which was accepted by the Japanese emperor after deliberation. Even though Japan was under the leadership of SCAP, while other countries such as China and Germany had the stake in leadership, the SCAP relied on Japan for governmental issues.

the United States led the Allies in the occupation and rehabilitation of the Japanese state ... The first phase, roughly from the end of the war in 1945 through 1947, involved the most fundamental changes for the Japanese Government and society.