What did the Japanese admiral mean when he stated after the attack on Pearl Harbor, “We have awoken a sleeping giant."

The Japanese admiral stated after the attack on Pearl Harbor, “We have awoken a sleeping giant."

This meant that the Pearl Harbor attack had woken up the United States to join World War II. The United Stares were initially quite uninterested and were staying out of the war until this incident which spurred them to fight back.

doesn't make any since

explanation:

mass production/ assembly line production