The US Treasury can print treasury notes. The FED can "print reserves" and banks create deposits from loans ( aka bank money). The Treasury notes are then sold and the US Treasury account at the Fed is credited.
When the Fed prints currency (say a $100 bill), what happens? Does the Fed just suddenly have $100 more than it did? Or does the Fed owe the Treasury $100? Or something else?
I don't immediately see a way that somebody (anybody) can print a $100 bill and still have assets and liabilities net out to zero...
When the fed create money is a liability for them:
https://www.federalreserve.gov/monetarypolicy/bst_frliabilit...
When you pay taxes, that liability is cancelled. The circle has to begin somewhere, and it begins and end with the government.
The government owe the liability to whoever come backs with that money to pay something (taxes normally). It will accept it as payment.
What is that something?
In particular, if you don't buy the whole premise (that dollar bills are US government liabilities), then RobertoG's statement (that "Money is an IOU. That is a promise of something.") is completely unconvincing by itself, without further support. And your "support" is not very helpful.
https://www.creditwritedowns.com/2011/10/currency-revulsion-...