If country A (China) purchases the debt of country B (US of A) then "purchase debt" in that context is the same as B "issues a bond" which is the same as B "gives a loan". Yes. To the best of my knowledge, yes.
> I don't understand how the US Treasury would not be liable for paying back the principal and interest on the bond.
The US Treasury is liable, yes - but here is the catch that is never mentioned in any of these articles - at what rate? All these bonds are maturing at different times and have different rates of interest, right? So what would be helpful is that rather than saying that country B owes country A n trillion in total is if we were told how much per month (or year, or whatever) it is costing to service the loan - that would make it real. Note, IANAE.
> I don't understand how the US Treasury would not be liable for paying back the principal and interest on the bond.
The US Treasury is liable, yes - but here is the catch that is never mentioned in any of these articles - at what rate? All these bonds are maturing at different times and have different rates of interest, right? So what would be helpful is that rather than saying that country B owes country A n trillion in total is if we were told how much per month (or year, or whatever) it is costing to service the loan - that would make it real. Note, IANAE.