It has been American policy for many years to accommodate the rise of China, but only within established international norms (i.e., not by imposing its will on smaller neighboring nations). The TPP is the latest, and perhaps most important, expression of that policy; it ultimately gives the Chinese the choice of isolating themselves or joining a club in whose rules it had no say.
President Obama is going to have a difficult task explaining the fairly subtle distinction between rules-based policy and Chinese containment to the American public and the rest of the world in the process of selling the agreement. For their part, the Chinese have never accepted the notion that they are bound to follow international norms in areas they consider to be their own territory, particularly since the rules, in their eyes, were made by hostile countries and are stacked against them. Don’t be surprised if more aggression in the South China Sea ensues, even though that, in a sense, would validate the purpose of the agreement.