Two men who carry the weight of half the world's economic output sat down this week in Washington — a meeting between Donald Trump and Xi Jinping that is as much about what is left unsaid as what is negotiated. For years, the relationship between the United States and China has been defined by accumulating friction: tariffs, technology bans, and competing visions of global order. That these two leaders are meeting at all, on American soil, suggests that even rival powers recognize the cost of pure estrangement.