One thing to remember is that the Philippines were more important as a port for US interests in the South China Sea which provided it with a reason to push for the Open Door Policy in China under Secretary of State Hays, so the US could get free trade access to the entire Chinese export market.

With regard to mercantilist economics, it worked remarkably well for European powers who could pull it off. The British maintained a large overseas empire which allowed them to import raw materials like oil from Iran, cash crops and timber from Africa, etc. The predominance of this empire over others began in the 19th century when it achieved new heights.

Look at the American Empire after the Second World War, there were huge fears by Dean Acheson, Paul Nitze, Averell Harriman, and others that the United States would fall into the same Depression that the war had rescued them from. This cohort told Congress that if Europe were not rebuilt the US would lose valuable export markets in Europe because Europe would be unable to earn the money to pay for US exports. Acheson and the Truman Administration used the fear of Communism in the wake of the Fall of China and the Korean War to get Congress to support Western Europe out of the fear of it falling to Communism.

I hope this helps.

Sources:

The American Age by Walter LaFeber

NSC 68 and the Origins of the Cold War by Curt Cardwell

It would mean raw materials are sold internally rather than exported. This in turn would ensure the industry needed to process raw materials is located in the colony or the parent country which is beneficial for security (self-sufficiency in the event of war) and taxation (you can't tax a factory not on your soil).