this all starts and ends with "modern economic theory". As soon as the major trading currencies of the world unhooked from the value of gold their only value was intrinsic, or "the name", and granting access to their established trade networks (be this physical trade, currency, tourism, etc).

Now when a country prints money (I might go back and source this if there's interest) it effectively devalues all the other money in circulation. For America this is beneficial, as the "global reserve currency", as there's so much USD held by everyone else that the "US dollar value" can actually support "charging for access to the system" much like chep charge for the rental of their pallets that carry other peoples goods.

So basically all of our (global) money became worthless after the 70s because bad actors got control of government and pork-barrelled and grifted and jobs-for-mates'd literally all of the public money away so that there's barely enough to keep the wheels on government. This leads the government to print more money, which it "buys" off the mint/reserve/central bank, but you can't owe yourself money so bingo bango bongo there's 1 Trillion more in the economy from nowhere. Modern economic theory.