Thumpalumpacus
Colonel
If the Americans do not join in the war at all the Japanese "win" big. If the Americans join in several months later with the Philippine bases undamaged and alert taking the Philippines so going be much harder and the Americans (in theory) can do much more damage to the Japanese supply lines. Japan has just tipped over to the losing side. To get the "win" they to do even better in sea battles and air battles than they did historically. Early carrier battles have to go to Japanese.
I don't know. That depends on whether or not we still have MacArthur's and Sutherland's mismanagement. It also depends on whether the Filipino Scouts can be expanded, better-trained, and furnished more and better equipment.
I mean, you make good points, but it requires the joint leadership in the islands to take advantage of the opportunity. Was MacA the kind of leader to make hay while the sun shines? Or does he maintain his unwarranted assumption of inherent American superiority?