United States must support international currency for its own welfare. Currency is material representation of people right, of value coming from human desire. If we haven't international currency, we haven't international recognition of foreign value. So international trade and financial commitments are risky. Value sold or bought in dollar by United States is uncertain for the rest of the world, so uncertain for United States. Because dollar is representation of american people rights to value, not of Chinese, Indian, African or European right.
Without international currency representing international common right to value, United States cannot measure the real value of its economy. If each person is single all over the world, for the place where it lives, the language it speakes, the people it likes, it is not realistic to make it use a currency of another country in its international relations. That's why American economy became unstable and so on world economy. IMF must become international central bank for international recognition of world common value. That's what Keynes recommended in Bretton Woods.