For more than seven decades, the United States dollar has been the world’s reserve currency, with a majority of international transactions using the greenback. CNBC’s Uptin Saiidi explains how it became so strong and explores whether its position could be threatened.B站UP主：新英文杂志Subtitle：You know this is the U.S. dollar. It’s the official currency of the United States and its territories, but, also, some other countries use it as their official currency too. In fact, the U.S. dollar has become the world's reserve currency.So how exactly did this become so powerful? More than $1.8 trillion of U.S. currency is now in circulation around the world, and it's believed that two-thirds of $100 bills and nearly half of $50 bills are held outside the US.In fact, the U.S. dollar is the de facto global currency, meaning it's kept by many governments in reserves and that
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