According to MarketWatch, the U.S. government itself owns 27% of the U.S. debt, with U.S. investors owning a further 32.5%. The Federal Reserve owns 11.2%, which is just a slightly more complicated form of the government owning it. So all that added up is 70.9% of the U.S. national debt that's owned essentially by U.S. interest.

As of 2018, they held about 5.6% of our national debt in the form of treasury bonds, but Japan also had 4.9%.

Also, in 2020, Japan overtook China as the largest foreign investor in our debt.