> making it exponentially harder for them to attack Taiwan
I fail to see how the sentiments of Vietnam or the Philippines have any bearing on the capacity of China to capture Taiwan. Talk is cheap, and neither country has taken any substantive steps toward a deterrence capability, let alone an improved one.
> The US basically has a barrier of military bases along the entire Chinese coast.
This sounds like something a PRC defense pundit would claim as justification for China's belligerency in the South China Sea. The few US bases in the region are north of the South China Sea, in Japan and North Korea. Take a quick glance at a map.
> The US also besties with Singapore, sharing a navel base there, where it could easily cut off China from middle eastern oil via The Straight of Malacca.
Singapore also has close ties with China, including joint military training: https://www.reuters.com/world/asia-pacific/china-says-will-c...
The "bases" the US has in Singapore are merely for logistics and training. India also has similar agreements for use of Singapore's naval bases, and India is not a defense ally of the U.S. Singapore has a few bases in the U.S., but they're likewise for training and nobody would claim they're a potential military staging ground.
Singapore isn't a defense ally of the U.S., notwithstanding their defense ties. As a vulnerable city-state Singapore desires to be besties with everybody, especially those who can exert pressure on Malaysia and Indonesia.