And I don't feel "it hasn't happened before". I tried to say it better in a post to Jerome above. The UK had the US seigneurage position a long time ago, and lost it, as their economy soured. So it could happen. Maybe you could comment on that post, and see if we have a disagreement still.
US consumers and businesses have been buying their goods from and outsourcing their services to cheap currency countries, which has stopped what would have otherwise been a natural devaluation of the dollar. As a result, the US current account deficit is now pushing $US800 billion, $US300 billion higher than when, as research house Bridgewater Associates puts it, "private sector capital gave up on the dollar in 2002". It is also the biggest financing task the world has ever known.
The world has changed a lot since the pound lost its status as the world's currency, which correct me if I'm wrong happened around WWII, when the entire world economy was effectively shattered anyway. The rise of asia and the rest of the developing world, globalization...I don't think there's any comparison.
