In December 2019, the U.S. national debt was $23 trillion. Of this, 29% was held by foreign investors and governments.

Which 2 foreign countries are the largest holders of U.S. Treasuries? What would happen if their demand for Treasuries declined? What would happen if they engaged in a mass sell-off? Consider the impact on interest rates and on the value of outstanding Treasuries as well as the economies of both the foreign countries and the U.S.

Does Puerto Rico hold U.S. Treasuries and, if so, how much?