From the Summary: "This report presents current data on estimated ownership of United States Treasury securities and major holders of federal debt by country. Federal debt represents the accumulated balance of borrowing by the federal government. To finance federal borrowing, United States Treasury securities are sold to investors. Treasury securities may be purchased directly from the Treasury or on the secondary market by individual private investors, financial institutions in the United States or overseas, and foreign, state, or local governments. Foreign investment in federal debt has grown in recent years, prompting questions on the location of the foreign holders and how much debt they hold."
CRS Report for Congress, RS22331