As far as I know US already invaded and capitalized China. There are so many US companies there. They even have Hooters in China. Both countries are benefiting from this relationship and they don't want it to change. IMHO, China won't invade Taiwan. If they do, it would cause political instability and hurting their economy, for no good reason. (Taiwan isn't as valuable as it used to be). China is not in a good geographic position for any type of instability. As for US being the world police, I think US does benefit from this--in a form of lower oil price, and more business for US companies. US could not retire from it's global policing.
US could still sell arms to those countries. That way, US could maintain peace while capitalize on it. If it fail, then get ready for nuclear war.