US debt has been this high before.

You lend someone money based on whether you think they can pay you back. People still buy US debt because the US is good with its promises.

It’s the same reason the US dollar is the reserve currency… the US govt knows how to keep it reasonably stable and has decades of success at it.

Does the US use this to their advantage? Sure. But it doesn’t matter… you just need to be better than the next guy. Just observe the 100 year history of many countries: their institutions 100 years ago are much different from today. No one likes uncertainty.