China holds $800b of US debt. It has some notional worth noting forex in euros or renminbi. If it's renegotiated into other forms and then revalued, they will hold less in renminbi or euro equivalents.
How does this differ from Greece or Argentina? Is this what the US economists and the federal bank really want?
A related question is how this would improve the Trump family debt and equity. I am guessing there is some plausible massive upside for Trump personally, not just his vision of the US economy.
Certainly after a US dollar is worth less $AUD things like Apple computers become cheap, assuming Apple doesn't reprice them...