"The Social Security Trust Fund owns a significant portion of U.S. national debt, but how does that work and what does it mean?"
https://www.thebalancemoney.com/who-owns-the-u-s-national-debt-3306124
"As headlines often remind us, each U.S. citizen owes a share of our currently $20 trillion public debt. But Americans also own approximately $14 trillion of that debt – as participants in Social Security, insurance policyholders, participants in pension funds, stockholders, or, more directly, by virtue of having purchased Treasury notes. “Treasuries” are very secure, and those not owned by Americans are held by foreign banks and governments that are glad for the chance to lend money, securely, to the United States."
https://scholars.org/contribution/why-there-nothing-scary-about-us-national-debt
"the property and assets of every living U.S. Citizen is pledged as collateral for the National Debt!"
http://viewzone.com/collateralx.html