The lack of any monetary rule to constrain the Fed and the lack of any convertibility principle, as existed under the classical gold standard, means the Fed has a monopoly on base money (currency held by the public plus reserves), the supply of which is determined by a small group of Fed officials who presume to be able to forecast the future.
But when Buenos Aires' economy began to reel from International Monetary Fund-imposed taxes, markets began doubting Argentina's willingness to maintain convertibility.