Closer to the latter.
This train ain't stoppin'
Agreed. Current interest on the US national debt is coming up on 25% of current total federal tax revenues.
When a household gets to the point of paying 25% of their income on interest from unsecured debt, where are they headed? Bankruptcy! How can a household pay down a debt that so large it's taking 25% of their income in interest?
A person might say "The household should be able to refinance their debt from short term, high interest rate loans, to longer term, lower interest rates." Yes, but the US already is paying an estimated 3.3% interest on its $35.8 trillion debt. That's already about as low as possible. In fact ,it lower than the likely rate of inflation going forward. That rate is likely to rise.
A person might say, "It doesn't matter. A government can just print money to pay the interest!". Yes, but printing money raises inflation, as has been known for millennia. Rising inflation raises interest rates, so soon the US will be paying much more than 3.3% inflation on the enormous $35.8 trillion debt, which will reach $40 trillion in barely two years.
The government will either have to print money and cause significant inflation, or they will have to undertake painful measures now to start getting back on the right track.
They will print the money. The inflation will get much higher.