During World War II did the Japanese ever attack the U.S. mainland?
Yes. On February 23, 1942, the oil refinery at Ellwood near Santa Barbara, California, was shelled by a Japanese submarine using its 5.5 inch deck gun. This was the first attack on the U.S. mainland. Then on June 7, Japanese soldiers invaded the U.S. Aleutian Islands off Alaska and remained there until American troops retook the islands in May 1943.