You hit upon a Major DETAIL ,you are correct ..They never printed the Money to pay the interest with ….The only way they can do that is to print “TREASURY NOTES” and enter the system by passing the FED ,instead of “Federal Reserve NOTES” John Kennedy tried that and you see what happened to HIM !
Barring that it means they have a ZERO SUM GAME for everyone that does find the money to pay interest ,that leaves that much LESS for the NEXT GUY and soon they have a CRASHING money Supply !
Thats the FEDS dilemma and the higher interest go the FASTER it happins and the Higher the DEBT goes the faster it happins ..
Thats exactly why a DOLLAR was as good as GOLD during the DEPRESSION …very scarce ..contracting money supply ,,very FAST …
Its NEVER good when the Dollar is as good as GOLD…its stops circulating and becomes a store of value instead of a circulating medium ..
The medium of exchange needs to be plentiful ..when it contracts its very painfull ……Thats why Milton Friedman called his book
“THE GREAT CONTRACTION” ……now you know !