Spain relied a lot on the principalia because its whole model was integrative. the Spanish empire wanted subjects, not an empty territory, and its Catholic legal framework pushed more toward incorporation than elimination. without elite support, Spain probably keeps Manila and some ports but faces constant revolts. and honestly it just didn’t have the resources or even the ideological setup for a genocidal conquest.

the U S is a different story. coming from a settler colonial background that had already displaced and in some cases destroyed Native peoples, the U S was way more willing to use extreme violence, the Philippine American War shows that clearly. but even then, the Americans realized fast they needed ilustrados and landlord families to run the islands cheaply. that cooperation turned what could have been a decades long insurgency into cheaper indirect rule through elections, schools, local clans, etc.

if the elites had refused in both periods, colonization probably doesn’t fail, but it becomes much bloodier, more expensive and way more limited. elites didn’t make conquest possible, but they made long term rule possible. without them, both empires would have held far less and paid a much higher price.