In response to the sinking of the U.S. gunboat Panay, FDR goes before a joint session of Congress on December 13, 1937, and asks Congress for a
declaration of war against Japan. Four years before he actually did so OTL.
The United States goes to war instead of taking the Japanese blood money.
The war goes badly between December 12, 1937, and April 12, 1938, but
the U.S. Navy fights back. By 1941, when the Japanese attack Pearl Harbor,
the war's already four-years-old. Allied forces go after the Japanese at Balikpapan and other battles in the Pacific.