Note, the units I listed as being in the PI in mid 1942 were mostly "on the water" when the Pacific war broke out. The second US division was in Hawaii. The first M3 Lee battalion was in LA waiting for shipment. There were an additional 40 P 40E enroute on the Langley. A Marine defense battalion similar to the one on Wake and Johnson atolls was scheduled for the defense of Subic Bay (the Naval station there). More National Guard units were being shipped too. One battalion of Texas National Guard artillery was already in the PI.
The US was gearing up for war big time at the end of 1941. There involvement was virtually certain sooner or later.