I've always heard people say that the US debt doesn't matter when the debt itself is denominated in USD.
It's the old saying, if you owe the bank $1,000 then you have a problem. But if you owe the bank a trillion dollars then the bank has a problem.
Especially when that trillion dollars was spent on an insane fleet of aircraft carriers.
This used to be true, but less so after the US started alienating the rest of the world with tariffs and other erratic behavior. The US military has also been revealed to be incapable of controlling the strait of Hormuz.
Except it's not a bank, it's a country with a few hundred million people that need to work and eat. Once the lenders have a problem, it would already be the end for Americans.
The quiet part you're not supposed to say out loud is the "if you don't use our currency to transact for energy and thereby let us tax it via inflation we'll regime change you" implication it comes with.
This idea is based on the fantasy idea of "it's fine because the US can just inflate away its currency to reduce its debts". This is also often used as an argument for why countries shouldn't join the Euro because they'd be giving up an important tool.
The reality is that purposefully inflating your currency to reduce your debt burden is going to upset your creditors just as much as if you just defaulted on your debts, but will have the added affect of crippling your economy with inflation. Look at how much Americans freaked out over a year or two of 6% yearly inflation. How do you think Americans would respond to 30% *monthly* inflation like in Argentina or Turkey?
It's not like lenders won't notice if the USA tried to print its way out of debt.