After the collapse of the economy in '29-30 there was literally no money in the system as US gold was all overleveraged in foreign markets. The only way to fund a recovery was to take us off the gold standard domestically to allow a fiat, but sovereign, debt that was no longer pinned to gold.
It was just a spread sheet entry that tracked the new money created in the private sector and balanced out (destroyed) any money entering the government sector as a first order accounting function. (Debt and assets similarly denominated must remain in separate sectors if they are to remain separate)
There wasn't really much of a change visible to the people except the government now could "afford" anything that was available and priced in US dollars. We stayed on the international gold standard for trade, but never looked back in our domestic economy. The need to ramp up for the war effort shortly after was also a factor in staying with our fiat system.
With an infinite supply of US dollars available to Congress to mitigate the effects of the depression the concept of taxing or borrowing for revenue to enable spending was made obsolete, as Ruml's paper stated. There is no "infinite+1" in math that would make Congress' ability to spend any easier. Nonsense left from the gold standard was never completely removed from political rhetoric, or even regulation however.
The one most confusing to the people is the requirement to issue Treasury debt to "match" any deficit spending by Congress. This makes it appear that investors are "funding" the spending, but it is actually the other way around. One cannot loan what doesn't yet exist. Treasury debt issuance is welfare for the wealthy.
The regulation serves the purpose of misrepresenting our debt, which is actually our national savings represented in Treasury bonds, and enlisting the people's support in a general "debt bad" campaign as people equate the federal government's budget with their own as "users" of the currency, not "issuers".
The "debt ceiling" is another particularly nasty regulation that both sides treat far too casually as it can actually do great harm if followed through with, despite being useless fodder to fool the rubes. This is also tied with the idiocy of a "balanced budget" amendment that is a thing in conservative circles again.
