The Philippines is strategically indefensible. It has an almost purely air-naval problem of defense, against a world power. It is completely dependent on maritime trade not just for its foreign trade but also its entire domestic economy.
Geography is everything.
Vietnam can defy China by daring it to invade overland, and can live off its ricefields until the Chinese get tired of the slaughter as the enemy has to fight through hundreds of miles of earthworks defended by cheap light infantry. But the Philippines has to defend every internal shipping lane, using the highest technology means in large quantities against air, missile and submarine attack, or it starves. Heck, its got such internal bottlenecks that knocking out a series of highway bridges could make Manila uninhabitable.
The Philippines is a third world country with a first world defense problem. It would take an investment of @50billion to begin to credibly address its problem. Its entire government budget though is $50Billion.
So it needs very powerful friends or it needs to bend. That is the problem of geography.
Yep. The decision to push the US Navy out of Subic Bay will haunt them for decades.