Why did Japan get into a war with the United States?
The Japanese didn't want to get into a war with the US. The plan was to take out Pearl Harbor, a major U.S. naval base, unexpectedly, thus crippling the giant and keeping them out of Japan's hair while Japan went on to conquer East Asia.
It was also the Japanese intention to take control of the Philippines which meant that they would have to oppose the United States at some point. They chose to make it an engagement on their terms as opposed to one where the Americans could have a strong showing.