Question: what event caused the united states to declare war and enter world war ii

title: German declaration of war against the United States
text: On 11 December 1941 , four days after the Japanese attack on Pearl Harbor and the United States declaration of war against the Japanese Empire , Nazi Germany declared war against the United States , in response to what was claimed to be a series of provocations by the United States government when the US was still officially neutral during World War II . The decision to declare war was made by Adolf Hitler , apparently offhand , almost without consultation . Later that day , the United States declared war on Germany . 

Answer: answer: Four days after the Japanese attack on Pearl Harbor and the United States declaration of war against the Japanese Empire , Nazi Germany declared war against the United States, which caused the United States to declare war on Germany later that day.