If these countries don't have growth they will be confronted with hard choices about whether to buy Treasuries or not. If they don't buy them we slide further and they lose us as an export customer. If they keep buying them it's less money to invest in their citizens and the possibility of explosive disapproval from citizens exists (especially China).
You have put your finger squarely on the issue there. These countries (many of whom have a trade and account surplus with the US) now have a really, really hard choice to make:
1. Buy US paper at pitiful yields, thereby allowing the Fed and Congress to possibly reflate the US economy, only to see a prolonged period of mediocre US consumption of their exports, or
2. Bail on the US as the engine of their economies by refusing to buy any more US paper (they don’t even have to sell the paper they have — just stop buying the flood of new paper), turn their account surpluses inwards and stimulate their own economies, but guarantee that the US consumer is nearly a non-existent factor in their exports for at least five years, possibly as much as 10 years.
CompSci people have a term for this type of “resource contention” in concurrent programming systems: “the fatal embrace.”