>>" [..] We built the system that way deliberately because bartering is not efficient"
Not really, the history of money doesn't support that theory.
>>"[..] it's increasingly clear that in the future, these positive and negative numbers will never add up to zero anymore,"
They don't add already, never were suppose to add. Where is the dollar coming from if not the deficits of government? The spending of money in the economy is what creates money. So, it's the debt of the public sector what create the money in the first place. You are complaining that excessive deficits are creating too much money, so you already agree with that.
>>"[..] Governments will have a hard time selling treasuries when no-one expects them to have any value in the future. "
That makes zero sense. The Central Banks can, and frequently do, determine the interest of the public bonds. Japan is the main example, but there are many others.
>>"[..] all value that is not recorded in tangible, useful assets or [..]"
A government tax every transaction in the economy, and can do it because it has the monopoly of force in that country.
If the USA government only accept dollars for paying taxes, there will be always (while there is an economy and they keep the monopoly of force) demand for the Dollar. The same is true for all the other countries.