Here are other things I found out concerning the South China Sea issue:
1. There are six claimants to parts of the South China Sea, including the Philippines and Taiwan, and they are against each other. Even Taiwan rejects Philippine claims, and both are allies of the U.S. This is probably the main reason why the U.S. has not been interfering.
2. China started incursions in the region when it fought against another claimant, Vietnam, in 1988. After it won, China started entering the Kalayaan Island group, and the U.S. did not act as well. By 2005, the other claimants had started building installations in the area.
3. The U.S. had for decades been attempting to to surround both China and Russia with dozens of military bases and installations following a "grand chessboard" strategy, culminating in Obama's attempt to pivot to Asia and wrest control of the region from China. The U.S. failed and can now do little, specially when the claimants have effectively taken control of the seas, including two international trade routes which they feared the U.S. would attempt to choke given conflict.
4. Filipinos are pro-U.S. and critical of China, but for some reason can't remember that they've been screwed many times over by the U.S., starting with onerous trade deals in return for independence, then support for the Marcos dictatorship, and after that inability to help the Philippines concerning China because the defense treaty between the U.S. and its ally covers only land territories and support is pre-conditioned by approval from the U.S. Congress.
5. China, as part of BRICS (with Brazil, Russia, India, and South Africa) and with forty emerging markets (including the Philippines and the other claimants of parts of the South China Sea: Malaysia, Brunei, Taiwan, Vietnam, and the Philippines), have been increasing in economic strength across around two decades, to the point that some predict they will dominate not just Asia but the global economy, and might even switch to a basket of currencies rather than rely on the U.S. dollar.
It is based on these and other points that some believe that the U.S., in order to get back control of the global economy, may eventually attack China: