China has big ambitions. It wants to overtake the United States as the world’s superpower by 2049, a hundred years after the Communist Party took power in Beijing. And this will be at the expense of the U.S., which unwittingly helped its strongest rival now closer to attaining its dream. This is the gist of a 2015 book, “The Hundred-Year Marathon: China’s Secret Strategy to Replace America as Global Superpower,” by Michael Pillsbury, an American China watcher who had served several U.S. administrations since the time of Richard Nixon in the 1970s.