General Doolittle led a raid against Tokyo and other Japanese cities to raise US morale.
Declared war.
Had to immediately react to violence.
Short answer: Pearl Harbor attacks by the Japanese
they droped nuclear bombs on japan
According to published reports, 2402 American lives were lost at Pearl Harbor. The attacks on 9/11 claimed 2977 American lives.
US counter attacks: Doolittle Raid & Guadalcanal.
While there were earlier attacks, such as the sinking of the gunboat Panay in China, the first full scale attack on US Forces was at Pearl Harbor, Hawaii on 7 Dec 1941.
They reacted almost immediately by going to war against Japan, the very day after pearl harbor the desicion was made to go to war
Attack the Philippines instead
Nevada
Pearl Harbor was the main base for the US Pacific Fleet.
Pearl Harbor provides shelter from storms at sea for the US.