As the United States marks the 250th anniversary of its founding, it confronts a new world order dominated by its relationship with China. In this wide-ranging series, we examine the pressure points and possibilities in those ties, from hard tech to soft power. In this article, Sylvia Ma examines the numerous financial links between the two economies that make a true decoupling a difficult affair. On a landmark visit to Beijing in 1986, the New York Stock Exchange chairman at the time, John...