The US isn't limited to just "several" drones. The limit to how many they can transport to the Philippines is how many they can build and transport by sea or air, which is enough to threaten any defense networks.
If the Philippines protests against the US after China retaliates, what's going to force the US to listen?
The US drone production rate is effectively infinite if China can't dislodge them from the Philippines and if the US can keep resupplying their forces there with regular shipments, which it can.
Easier said than done. There's also cargo planes. China can't shoot down cargo planes landing on the eastern coast of those countries, let alone ships.