Why did the US join WW2?

The Japanese attack on Pearl Harbor on December 7, 1941, ended the debate over American intervention in both the Pacific and European theaters of World War II. The day after the attack, Congress declared war on Imperial Japan with only a single dissenting vote. Germany and Italy— Japan’s allies—responded by declaring war against the United States. Faced with these realities and incensed by the attack on Pearl Harbor, everyday Americans enthusiastically supported the war effort. Isolation was no longer an option.