How safe are U.S. Treasury Bonds?

I discuss the default history of US Treasury bonds.

References:
- "Has the U.S. Government Ever Defaulted?" by Andrew Austin, published 8 December 2016 in the Congressional Research Service [https://sgp.fas.org/crs/misc/R44704.pdf]
- "The US has never defaulted on its debt — except the four times it did" by Alex Pollock, published 7 October 2021 in The Hill [https://thehill.com/opinion/finance/575722-the-us-has-never-defaulted-on-its-debt-except-the-four-times-it-did/]