Conditions in Asia were becoming poor and emigres were searching for better locations to live in, possibly meaning the weather had become awful and therefore made their homelands intolerable.
Pearl Harbor brought the U.S. into WWII, which changed the reason of why we would fight in the war, and potentially changed the outcome of World War II. Before Pearl Harbor, the United States had declared to "remain a neutral nation" in the war by President Franklin D. Roosevelt.
