Source: I worked on a fall detection app for the Apple Watch last year.
And the debt is owned at ~50% by the government itself or the Fed and ~20% by various non-federal investors (pensions, mutual funds, local governments, individuals) with the rest being owned by various non-US entities.
Things are different for the federal government. It's an institution of last resort, so the normal ways of thinking about personal finance don't apply. It can't open a "savings account" anywhere, because every other institution on Earth is smaller and less reliable.
The ambiguity there is abused by many companies on the fringes of consumer health and cosmetic products.
> A 510(k) is a premarketing submission made to FDA to demonstrate that the device to be marketed is as safe and effective, that is, substantially equivalent (SE), to a legally marketed device that is not subject to premarket approval