From what I read, the main reason the Spanish controlled Nueva Ecija, Upper Cagayan and Tarlac as well as the other parts that remained pagan up until 17-18th century is that they settled it with immigrants from the Spanish controlled parts which are the coastal areas, what if the Spanish were defeated by the inland tribes expelling the settlers and repeatedly defeated them gaining a truce with the Spanish like what happened to the Igorots, what would happen to the Philippines in the long run?
What would be the consequences?