it's not useless, it's good if there's a gentlemen's agreement, no nuclear, besides, at this point any nuclear strike on someone else, and it's really a strike on yourself even if they don't respond.
If you don't think we can't then you should know why. America. Anything against the Philippines may trigger a bigger conflict, even assuming it won't, China's main goal isn't South China sea, or any territorial dispute, it's economy. Being 12,000+ and in the higher income bracket is the utmost importance to China right now, we should reach that point no later than 5-6 years.
We can't be a leader in the developed world without being in the developed world. China has no interest in being a king of children(sounds better in Chinese). So if you want my answer it is fear. While some see fear as cowardly, fear is what keeps people alive and really only available to those with sense. Iraq and no fear with the US in the Gulf war see what happened.
Bismark had fear of French and British, and see how good he made Prussia.
Also 20,000 American troops can do a lot, but not against equally equipped men, being more experienced, your command structure and such would be better and a few other areas. But due to the type of war America's been in, like light infantry charging tank positions, and lack of close anti air for armour, like our HQ-17. If you do that with China, believe me Chinese soldiers won't be like Iraqis and run for the hills, before battle.
Look at WW2 Japan, your experience can be your undoing.
Okay you said its about economy and yet you have territorial disputes that are related to the economy. Why do you have disputes with the other countries then? Please enlighten me.
You have to remember that we just don't send infantry with rifles only but anti-tank weapons like the Javelin and TOW for example. And there are naval bases being set up a so you have the U.S. Navy to contend with. And indeed WW2 has taught us a lesson about the human wave Banzai by the Japanese.
What can we say? Congratulation to the Philippines. What a country do to their sovereignty is part of their business. If they decide to let US pimp them, then it is their choice. We will never allow the US to touch any part of Greater China territories (HK, Macau, Taiwan). Those are prohibited from having foreign troops station. It's a red line draw by our people.
Of course China won't allow it. They are going against the other countries in Asia that are going against them with U.S. help. Makes sense right?