that's not how debt works on a national level.... it's not like personal debt at all

I know this is true when the debt is issued by the currency issuer & denominated in that same currency, such as in the case of the United States.

Is that also true in the case of say, Italy's debt denominated in Euros or Illinois state debt denominated in USD? I have been meaning to read Steve Keen's work on this

when Italy was on the lira yes, with the Euro no. Look at how the Greek crisis unfolded.

the 20T will have to be paid back. Unlike personal debt the fed can just print the money. There is currently around 6T in existing money supply (though I havent checked recently).

The question is how will the debt translate to increased money supply over time (inflation).

> Unlike personal debt the fed can just print the money.

A part of why the Fed (and the same is generally true of independent central banks generally) exists (and why the Fed system is comprised of large private banks) is to provide a check (and, more important, confidence among lenders) against Congress simply monetizing the debt by separating the locus of decision making for monetary policy from that for fiscal policy.

Historically that often doesn't really happen with such debts. Instead the debt falls a percentage of GDP due to GDP growing, at least in nominal terms.

It is happening, though. Especially now with tax cuts and increased spending.