Answer

1. California workers would be against Japanese immigration due to economic competition for jobs.2. The headline in the Japan Times and Mail calls the Senate vote a "Declaration of War" because it was seen as a hostile act towards Japan.3. There could be a possible connection between the Immigration Quota Act of 1924 and Pearl Harbor, as the act may have fostered a hostile environment towards Japan.

Explanation

1. The anti-Japanese sentiment in California during the 1920s was primarily due to economic competition. Many Japanese immigrants were willing to work for lower wages, which threatened the livelihoods of local workers. This led to opposition from labor organizations.2. The headline in the Japan Times and Mail calling the Senate vote a "Declaration of War" likely refers to the Immigration Quota Act of 1924, which severely restricted Japanese immigration to the United States. This act was seen as a hostile act towards Japan, hence the headline.3. The Immigration Quota Act of 1924 and the attack on Pearl Harbor are connected in the sense that the act fostered a hostile environment towards Japan, which may have contributed to the negative perception of Japan in the United States. This hostility could have been a factor in the U.S.'s reaction to the attack. However, it's important to note that the connection is not direct, and there were many other factors at play in the lead-up to Pearl Harbor.