Answer
Demand for euros
Work Step by Step
So when the US exports goods to foreign countries, the foreign countries must have to pay in US dollars.
Therefore, foreign countries are supposed to exchange their currency for the U.S. dollar, which they can do at foreign exchange markets.
Hence, the US will have a stock of foreign currencies, which they can use whenever they purchase imports from those countries.
When U.S. airline buys Airbus planes from France, there will be a Demand for euros (Americans need euros to pay French exporter).
