Philippines is very strategically located. If it plays its card right, it can have very beneficial military relationship with the US. The military relationship can then transform into mutually beneficial trade relationship.
In your opinion, if US and Philippines were to get back to their good old relationship, and after that, if hostilities were to break out between Philippines and China, would US come out to Philippines aid?
Yes. But the US will not directly clash with China. What will most likely happen is that the US can make the pain so high for China if it militarily attacks the Philippines.
What it means is that the US will extend all possible military support to the Philippines to allow it to inflict serious casualties and damage to attacking Chinese assets. The US will also throw its diplomatic weight to isolate China. It will no doubt impose serious economic sanctions on Chinese officials, companies and even government instrumentalities.
Perhaps the most direct action that the US military can do is to mix US personnel with Filipino soldiers in operating transferred US military assets. The US can also do covert but always deniable actions like sabotage or cyber attacks on Chinese targets.
In other words, the US will do everything not to end up directly fighting China since both of them are nuclear powers. A direct war between the 2 most powerful countries in the World would be WW3. I don't think that would be in US' intetest, or even the Philippines'.
The bottomline is that it is in US' national interest to prevent China from overpowering the Philippines. It is also in US' interest to make it known to its allies in Asia that it is ready to uphold their alliances. If the US do not come to Philippines' aid in case of open Chinese military aggression then that will be the time that US losses influence in Asia.