Possible alternate outcome leading to Philippine Statehood
Greetings everyone, this is my first post so please be gentle.
I have put some thought into this, but I think there is a way for the Philippines to have remain a part of the United States into the 21st century. The point of divergence would be at the beginning of the Philippine-American War and would be that the American Generals who were governing the former Spanish possession would not do what they did in the OTL which is co-opt the ruling oligarchy that had formerly supported the Spanish governance, and instead advance land reform and appealing directly with the populace through similar operations that they did in the OTL in creating an all access education system, among other things. By doing so it will weaken the position of the oligarchy, who under the United States forces have less ability to advance their continued economic dominance and thus drive them into the arms of Aguinaldo's First Republic.
Although Aguinaldo gets a boost in funding from the oligarchy, with the United States forces controlling the vital sea trade routes by increasing its naval presence, the oligarchy's funds dry up creating and the funding of the First Republic forces dwindles coupled with losses on the battlefield and lack of support from the larger non-oligarchy populace causes a similar outcome for Aguinaldo's First Republic. United States, as in the OTL establishes an insular government, but it takes longer, and thus the American forces do not start to make in roads into the primarily Muslim Southern Philippines until later than the OTL. A further consequence of the change in policy is that the United States becomes less reliant on Volunteers, as overtime more Filipinos seek to join American forces first through the Philippine Scouts of the United States Army, who as time passes become the predominate fighting force (by size) of the American forces.
By the time that the United States begins to become effective in the Southern Philippines, the Great War occurs and the United States instead makes treaties with the remaining still fighting Muslim sultanates. In doing so the sultanate treaties create a situations similar to that of Native Americans and a section of the Bureau of Insular Affairs creates a new Bureau of Sultanate Affairs in order to manage the relations between the American Philippine Insular Government based out of Manila and the Sultanates in the South.
In the rest of the Philippines, the weakened oligarchy end up in a situation similar to the landholding Mexicans and Spaniards following the end of the Mexican-American War, where they were land rich, and money poor. Furthermore, given land reform, the former virtual serfs of the oligarchy own their own land, and have received training through the Insular Government making them even more independent from the oligarchy's influence, and more interested in continuing the improvement of their condition under the system created by the Insular Government. As in the OTL the Insular Government establishes a legislative branch, and rather than it being dominated by members of the oligarchy it is instead controlled by members of a new larger vibrant middle class created by a Pensionado Act that is far greater than in the OTL, many of whom come from families that were not members of the oligarchy. Additionally, due to the land rich, money poor situation, the oligarchy in order to attempt to salvage an economic position in the new growing economic environment before Black Tuesday the oligarchy in order to gain liquidate begin selling assets to the members of the new middle class and to investors from CONUS and the Territory of Hawaii who see similar economic opportunities as they did in the Kingdom of Hawaii. Therefore the oligarchy families are sidelined from a large part of the newly vibrant economy, and Manila becomes an even more vibrant "Pearl of the Orient" and rivals that of Honolulu in stature. Moreover, due to the reforms the growth of the communist rebel movements were stymied until World War II.
Unlike in the OTL, as the Philippine Scouts have shown their battle ability against First Republic forces and the Sultanates, prior to the sultanate treaties, the Scouts become the cadre of a newly formed Philippine National Guard who are called upon for service during the Great War. This increases the visibility of the Filipino in the eyes of the American public, along with those Filipinos who become economically successful who grow out of the pensianados and the universal education system that was established earlier. There are still the Filipino aqua and agricultural laborers who migrate to the United States, who struggle for acceptance as in the OTL, but are joined by more economically enriched middle class who follow them in order to provide them services funded through the wealth created in the Philippines. Ultimately what this creates is a weakened oligarchy, an new larger middle class, a better educated lower class, and a slowly growing (from the two latter groups) non-oligarchy aligned higher class.
As in the OTL, the Great Depression occurs and Filipinos who migrate to CONUS face the increased racism that occurred during that period, but instead of as occurred in the OTL where the oligarchy used the period to push for independence, the United States looks to move the Philippines towards more integration in order to begin greater taxation of the Philippines. This is done to increase economic activity to hopefully soften the economic blow that is occurring, and to increase funds to the Federal Government in order to help pay for the New Deal programs that are occurring in CONUS. Therefore a Commonwealth of the Philippines is established but without the independent driven mindset as was the case in the OTL, but more as a stepping stone to political equality with CONUS and hopefully statehood.
Events outside of the Philippines occur as they do in the OTL, and Japan begins their Second Sino-Japanese War, and the United States begins their economic embargo leading to the increased possibility of hostilities. However, unlike in the OTL, with decreased graft, increased economic vitality, and a more military experienced populace the American Phiippine Commonwealth forces are not the shabby newly formed ill trained force that it was in 1941 as it was in the OTL; rather, the Philippine Division is made up of well trained Philippine Scouts, and the Philippine National Guard (who in the OTL was disbanded after the end of the Great War) is as well equipped and trained as their CONUS counterparts. Like in the OTL the Japanese strike the American Battle Fleet anchored in Pearl Harbor, but also strike harder at the American Asiatic Fleet anchored in Manila Bay.
As in the OTL the Philippines is swiftly cut off from logistic supply lines due to increase IJN activity. Furthermore, the USAFFE forces, knowing from intelligence from the Second Sino-Japanese War, that the Japanese Army is battle hardened and not a force to be trifled with, instead of going with War Plan Rainbow 5, instead follow War Plan Orange from the beginning of hostilities and martial forces and supplies in to the Bataan Peninsula redoubt as wel a redoubt created on Mactan Island across from Cebu City. The oligarchy aligned population, a minority population, believe the Japanese "Greater East Asia Co-Prosperity Sphere" message and feed intelligence to the Japanese along with the small Japanese diaspora and some of the Sultanates. The oligarchy aligned groups see it as a chance to regain their former dominance of the Philippines, and the the sultanates who support the Japanese believe it's a chance to remove themselves from nominal Manila and Washington control.
With the supplies and fighting force concentrated rather than dispersed as had happened under the OTL disastrous War Plan Rainbow 5, when the Japanese finally made landfall, and began to occupy territory, they were faced with stiffer resistance than what occurred in to OTL. Rather than late December being a route in Luzon, it was a slower moving delaying action leading well into early February. Unfortunately, as occurred in the OTL, even with the increased supply in the redoubts, the USAFFE forces could only hold out so long. As occurred in the OTL, further efforts to control the Philippines by the Japanese forces did not occur until after the end of the Dutch East Indies campaign. With the OTL, Japanese forces began a renewed offensive in April 1942, but unlike the OTL USAFFE forces were able to hold out longer. The first to fall was Mactan Island whose water supply was sabotaged in May 1942, leading to an increasing desperate situation. Bataan fell in July 1942, with MacArthur and the Commonwealth government leaving the islands in late July by submarine, and Corregidor falling in mid August 1942.
Following the final collapse of American/Filipino forces in the Philippines, the Japanese established a puppet government headed by the oligarchy and those sultanates who aligned themselves with the Japanese. Both groups used their new power to brutally seek revenge upon those whom they believed wronged them: the non-oligarchy wealthy, middle class, non-Japanese aligned sultanates and lower classes. This became a situation similar to what occurred with the fall of the Republic of Vietnam, but far briefer. Unfortunately, for the Japanese aligned oligarchy and sultanates the longer than OTL Philippine Islands Campaign served to make less troops available of the Japanese Army elsewhere, and thus gains by the Japanese Army from April to August 1942 were marginally less than in the OTL (with the greatest impact occurring on New Guinea).
The remainder of the war concludes much as it did in the OTL, but the war's aftermath differs. Due to the severity of the actions of the oligarchy and Japanese aligned sultanates, their leaders are seen as equals in the Philippines as the Japanese forces, and justice falls swiftly and more harshly than the OTL. Additionally, as the Commonwealth isn't seeking independence, American rebuilding efforts of the Philippines is greater than the OTL, with more funds being allocated, less graft occurring, and a renewed middle class strengthened by an increased due to the GI Bill educated former Commonwealth forces veterans.
Due to the sacrifice which occurred in the Philippines was many folds greater than that occurred in Hawaii or Alaska, the push for political equality with other sub-national entities grows in the Philippines. Due to this, in 1946 the United States upgrades Filipinos from U.S. Nationals (a status that was not lost with the creation of the Commonwealth as occurred in the OTL) to U.S. Citizens, that is except for members of the oligarchy and former Japanese aligned sultanates, who eventually are granted their U.S. National status again sometime in the 1950s. On June 12th, the Philippines becomes the United States' 50th state, before Hawaii becomes the 51st state as in the OTL in August of the same year.