As we know since the gold standard was eliminated in 1971 by Richard Nixon, the US govt kept printing enormous sums of money in the form of debt. Basically Americans have been buying goods and services from India and China literally for free by printing infinite sums of USD. And since US govt has the sole right to print USD while USD is also the currency used for import/export , meaning Americans could buy anything they want from any part of the world as much they want.