Early Philippine independence would not remove the Japanese threat

How would relations with Japan change if the United States handed the Philippines back to the Filipino people in 1940?

Japan would likely wait until the Americans had withdrawn and then manufacture a reason to invade the newly independent Philippines.

Early independence would probably not protect the Philippines from Japanese expansion. The prediction is that Japan would wait only a few months after the American departure. A fabricated justification would then provide the stated reason for invasion. In this scenario, the American presence is a deterrent obstacle; Japanese interest in the islands does not depend on it.