I expect if they do not attack the U.S. on 12/07/41 as they did historically, it will be at most another six months before their fears become reality, and the United States intervenes, but on their terms, and more thoroughly mobilized and ready.
If US participation in overt war against Japan is pushed 6 months to 05/07/42, how much more mobilized is the United States, compared with both a) OTL 12/7/41, and OTL 05/07/42? How much of a trans-Pacific fleet train capability is built that can break through to relieve the Philippines by 05/07/42, compared with the (zilch) existing in 12/7/41, and (not much more) existing in 5/7/42? How much of limited US Army and Army Air Corps global assets and fleet assets will have been committed to the Philippine islands and Asiatic fleet compared with both the position of 12/7/41, and competing missions on 5/7/42 like Atlantic convoy protection, protection of the Western Hemisphere neutrality zone, training up the enlarging Army, and protecting the vital Alaska-Hawaii-Panama triangle in the eastern Pacific? How much can the the Philippine Commonwealth Armed Forces mobilize and arm up in the 6 months from 12/7/41 to 5/7/42?
Will MacArthur remain in place, and will plans improve or at least be made un-ruinable by bad command execution due to materiel plenty by May 7, 1942?
Some of the biggest potential advantages for Philippine defense come from the ability more time provides to mobilize local resources and to insert in more resources from the outside.
However, over the same 6 months, the Japanese are also gaining some resources in terms of combat experience, capture of Thailand, Malaya, DEI (& oilfields), Papua New Guinea, and Solomon Islands, possibly Burma, defeat of local British, Commonwealth, and Dutch forces defending those locales, and the ability all these newly captured positions including air and naval bases provide to launch multi-axis attacks anywhere along the 360 degree circumference of the PI.
If, on reflection, you think US-Japanese peace can only hold out only 4 more months instead, to March 7, 1942, OK, adjust all those values and answers accordingly.
How long does the war's start really need to be delayed in months---or years, for the US to be able to declare war, confident it can hold out and relieve its furthest outposts without sacrificing whole major units, major provinces, and major battles, take the offensive initiative and hold it until the end?