What were the causes and consequences of the Japanese American internment program?

Mostly fear that there were among the Japanese population in the USA, people who would help Japan in its war against USA; there was fear in America of a Japanese invasion of California.

Another reason held by a few people was fear that mobs of Americans might attack Japanese residents in USA, and so, these few people thought, the Japanese needed to be put where they could be protected.

During World War I, there had been a lot of fear in America of German-Americans, but other Americans saw that they were loyal and by the time of World War II, were not so worried about them as about the Japanese-Americans.  Also the Japanese looked different so that there was more fear of them (that is probably racist) and they were more likely to become a target of mob action if left unprotected, since it was easy to identify them by sight alone.