If the global market enters another downturn and the USD falls, the US could actually get downgraded. That would increasing the cost of this debt, and make it m

If the global market enters another downturn and the USD falls, the US could actually get downgraded. That would increasing the cost of this debt, and make it more painful to continue with a budget deficit. Essentially the US is riding on its reputation, but as good as that reputation is, as debt continues to raise relative to GDP international banks may grow wary of loaning, or simply want to diversify if they have a lot tied into US bound debt.