DENVER – Twentieth-century American statecraft produced Dean Acheson, Henry Kissinger, Richard Holbrooke, and many others who balanced the power of the United States with its responsibilities to develop key relationships, solve problems, and build international structures. “Twenty-first-century statecraft,” we have been told repeatedly, promises to go further and deliver more, for now US diplomats – and those of other countries – can use Twitter, Facebook, and other social media.