Was the Army of the same opinion as the Navy that the PI were lost no-matter-what, with a full-on Japanese attack? How deeply did the Army game out how to extend the campaign? (for example, a common AH theme is for the campaign to carry on in other parts of the archipelago, either by USA and Filipino uniformed soldiers, or as guerillas as historically occurred)
The Army was so reduced from 1919 it had nothing to defend PI with. Congress funded some Coastal Artillery installations. a 1920s era Army Air Corps installation, and the Phillipino Scouts at regimental strength. In the US the Army had four infantry and a cavalry division funded at maybe 75% strength, a few other divisions funded at half strength. There was a field brigade in Hawaii & what amounted to another brigade @ Panama. the Coastal Artillery still had a lot of installations, partially because the made for good pork barrel projects what with all that concrete, steel, & labor. The National Guard with its 25 Divisions was popular. The pork barrel opportunities were large as every county could have a small armory, and every city a big one. & all those Great War training camps could be made into permanent National Guard training sites generating more guvmint money for local construction companies.
All the above was in the 1920s. In the 1930s the Army had its field forces slashed to where the standing Regular Army consisted of four half strength divisions, a cavalry division of reduced brigade strength, a experimental mechanized brigade, & reduced brigades of a couple battalions each in Panama, Hawaii, & PI. The Coastal Artillery batteries were manned as low as 25% strength. The Army Air Corps was reduced to a organization for training pilots and testing new aircraft, with no meaningful combat capability. Every other division or corps was nothing more than a cadre. Mobilization for war revolved around activating approx 60,000 reserve officers and recruiting/drafting however many 18-36 year olds you needed.
I have not found details for the Army in WP ORANGE. There was a Joint Board established in the 1920s where tiny group of Army and Navy officers planned for combined operations in a variety of wars. ie: WP TAN, YELLOW, GREY, BLACK, RED, CRIMSON, GREEN, ect... ect... ect... I suspect ORANGE served as the model for most & most were neglected other than as War College & Naval College material. I did find a third hand source that claimed the Army intended for WP ORANGE to have 50,000 men equipped and trained for overseas service by Mobilization Day +180, & 100,000 by M +365. Since the USN did not plan to start offensive operations until after a year at the earliest that sounds about right.
The USN did have a couple of Expeditionary Brigades organized. Mostly Marines these were true combined arms brigades, with their own logistics element. They included a composite aircraft group, engineers, armor, artillery, HMG companies, and some rifle battalions. There was one of these on each coast, & the wherewithal to organize a couple more should war occur. These two Expeditionary Brigades & maybe four Army infantry regiments represented the only ready ground forces from circa 1925 thru 1938. In 1938 Congress finally provided for 1939 & 1940 funds to return the Army field forces to their 1920s strength.