On a September morning at Joint Base Andrews, Donald Trump welcomed Xi Jinping in a meeting that carried the full weight of two civilizations testing whether rivalry and dialogue can coexist. The encounter came at a moment when the US-China relationship had hardened into something resembling structural estrangement, with trade, Taiwan, artificial intelligence, and Iran each pulling the two powers in opposing directions. Trump wagered that the ancient art of face-to-face diplomacy might accomplish what years of institutional negotiation had failed to achieve — a pause, perhaps, in the drift tow