Why did the United States declared war on Japan?

Or

How did the attack on Pearl Harbour bring the United States into World War II?

Or

What incident brought USA directly into Second World War?

On 7 December, 1941, Japan attacked the US Fleet based at Pearl Harbour in Hawaii. Japanese naval and air attack destroyed 188 aircrafts, many battleships and naval vessels of the United States. More than 2000 sailors and soldiers lost their lives. This attack brought the USA into World War II. On 8th December, 1941 USA declared war on Japan.