Very interesting question -- and the answer is in the page you linked to, near the bottom!
Civilian dead were 9,512 United States Merchant Marine personnel, details given at USMM website; and 1,704 American civilians interned, by the Japanese(1,563) and in Europe (168), which are the subject of a U.S. Congressional Research Service report. During the Attack on Pearl Harbor 68 U.S. civilians were killed by friendly fire and 6 U.S. civilians were killed in Oregon in 1945 by Japanese balloon bombs.
