Yes it was agreed upon that the US Dollar became the underpinning of international finance at the Bretton Woods conference near the end of WWII.

https://en.wikipedia.org/wiki/Bretton_Woods_system

This has a link to the PMoney episode you're thinking of, as well as a more recent discussion of the economic fight other nations possibly trying to supplant or at least be adjacent to the dollar as a reserve currency.

https://www.npr.org/sections/money/2019/07/30/746337868/75-y...