I personally don’t buy it. When other country’s start divesting from US treasury ties, the party will be over. Already prices are rising faster than income. What did Germany, Zimbabwe, and Argentina, Venezuela, etc. do wrong, that the US is doing right?
Think about Carland, a country that makes lots of nice cars, and largely sells them to the US. Imagine the US decides to print a bunch of money, weakening our currency relative to Carland's. Carland's cars now cost more for Americans to buy. This might sound nice at first (for a Carlandian car peddler), but in reality what's going to happen is less cars are going to be sold, and your cars are likely to become less competitive than those from other countries. So the Carland government has a major incentive to try to weaken their own currency, and start doing exactly that. So other countries effectively end up absorbing much of our inflation, helping to greatly minimize the impact of any given batch of money-printing.
So if the USD hits a point where we're no longer able to effectively export our inflation, the result's not going to just be inflation. That's a SHTF moment, because it means we'll have reached a point where we're inflating so much that other countries simply can't afford to absorb it without or imperiling their own economies, or have become okay with not exporting much to the US. Given how extremely dependent we are on imports, this is going to be a catastrophe.
Beyond this there are lots of self-feedback effects to consider, especially with borrowing, but this post is already long enough!
[1] - https://search.brave.com/search?q=exporting+inflation&source...
That's really the key thing. What level is sustainable? I've come around to the idea that the main danger of deficit spending is inflation (because of the idea that government debt is private sector wealth).
The big levers the government have access to are spending and taxes. The first adds wealth, the second subtracts. In this way, government debt is really nothing like household debt that you and I have.