I read a book in my library back then when I was in high school. The PCA was still using M1917s and M1903s. Even Tommy guns were only issued to the Philippine Scouts. The MGs at this period were the M1917 Browning watercooled version. The M1917 Browning has become an iconic symbol of resistance against Japan here in the Philippines.
Difficulty is there weren't enough rifles to go around. a number of units lacked one rifle per soldier. Many of the ones WITH rifles had no training in using them.
MacArthur, Field Marshal of the Philippine Commonwealth, screwed pooch by the numbers.
Re: Manila - The worst possible thing would have been to try to fight inside the city. Beyond the massive number of civilian casualties the American forces were poorly equipped for urban combat (low on grenades, sub-guns, even explosives) and the Japanese were not going to try to hold down civilian casualties like the Americans tried in 1945. Worse the force in Manila wouldn't even be able to fall back to Bataan when the time came.
Also, unlike Stalingrad and Leningrad, which stand out as examples of cities that resulted in long term sieges that extracted heavy losses on enemy forces, the Japanese can readily surround Manila, something that impossible with the two Soviet cities. Japanese forces will simply surround the city and pound it with artillery until the defenders surrender. Once that happens its going to be "Rape, Loot, Burn, Kill" and IJA field officers will just let it happen.
The ideal defense of the Islands consisted exclusively of preventing the IJN from using Manila Bay for as long as possible. As soon as the war started the entire effort should have been to move everything to Bataan. There wasn't enough firepower available to stop potential lands at all the potential landing beaches, and there wasn't enough transport to properly react once the enemy committed, and worst of all there weren't enough trained men to even do an extensive delaying action.
Disperse the fighters, move the bombers to the south, along with enough fighters to defend the air fields, to where the heavies can conduct strikes to the north while being beyond easy reach of enemy aircraft. Send most of the Scouts from Luzon to the other Islands to get resistance cells started and make the Japanese bleed. Do what you can with the "B" and "C" units with some stiffening from some Scouts and maybe parts of the 4th Marines and buy whatever time you can get to allow the rest of the fore to prepare. Most of the regulars and the better trained Commonwealth Army units, along with the heavy weapons, go to Bataan. Evacuate the civilian population (don't want a bunch of innocents in the middle what hopefully will be a year long siege that is likely to get medieval before all is said and done) and start preparing defensive lines while dispersing supplies. Once the Japanese show up make them earn every foot. Wainwright will be able to hold the Peninsula for most of 1942 (there were enough rations in U.S. military warehouses to support 50,000 troops for at least a year). All it really does is knock the Japanese timetable off the table, but that's plenty.