This week the world learned that economic "decoupling" from America is a myth. The next lesson to re-learn is that the Federal Reserve's monetary mistakes have global consequences, and that one result of the Fed's great dollar miscalculation this decade has been a dangerous breakdown in world monetary cooperation.

Look no further than the European Central Bank, which was notably absent when the Fed made its emergency rate cut amid falling global stocks on Tuesday. In testimony Wednesday before the European Parliament, ECB...