Another reason, possible related to all of the above: if the USD sharply declines in value for some reason, its trade deficits with many export-dependent econom

Another reason, possible related to all of the above: if the USD sharply declines in value for some reason, its trade deficits with many export-dependent economies (e.g. China) will also decline and perhaps even become surpluses. Those who run such economies /really/ don't want that to happen.