One thing that the Americans have going for them ITTL, unlike IOTL, is that the P40's from Clark now have the chance to exploit the G3M Nell bomber's (and by extension nearly every Japanese fighter and bonber throughout the war) weaknesses, which was the bomber having no armor whatdoever and no self sealing fuel tanks, and those two combined with .50 cal machine gun rounds from P40's make for a raging aircraft fire. Also, the reason for the massive amounts of bombers in the strike forces was the fact that the bombing sights on the Nell were basically obsolete by 1941, and as a result, the accuracy suffered. The Japanese did a stopgap measure of having massive waves of bombers, but didnt rectify the problem either.