Answer:
The Japanese Attack on Pearl Harbor.
Step-by-step explanation:
The main reason America joined the Second World War, was due to the Japanese Attack on Pearl Harbor. This prompted suspicions of Japanese people currently residing in America. These suspicions included that they could be spies or s*icide bombers. These suspicions were the main reason for the Japanese Internment Camps, as a way to keep the Japanese under the close watch of the American government.