Someone already wrote a answer to the question the same as but with different wording; here you go.
Answer:
I would say into WW1 because of the Zimmerman affair.
Explanation:
United States entered the WW1 in 1917, although for three years they were not officially involved in it. But, then a telegram was intercepted, in which an official letter was sent to Mexico by German authorities.
According to it, Mexico was to declare war on United States, while Germany will support them in the war efforts.
Many historians are doubting the reliability of this document.
where the heck are the options
After, the defeat of Japan the United States led the Allies in the occupation and rehabilitation of the Japanese state. So, between 1945 and 1952 the U.S. forces led by General Douglas A. MacArthur enacted widespread military, political, economic and social reforms.
