I presume that he tells them that they have to do something about their current account *surplus*: the U.S. has low inflation and (near) full employment--the trade imbalance is driven more by a depressed Europe whose imports are too low than by an overly-exuberant U.S. whose imports are too high.
But if they don't, then we are likely to see a large and rapid depreciation of the dollar sometime in the future...
Brad DeLong