Well, the point where continuing to incur obligations with no chance of ever repaying them (resulting in escalating interest rates as investors price it in more

Well, the point where continuing to incur obligations with no chance of ever repaying them (resulting in escalating interest rates as investors price it in more and more), will become untenable, may arrive. What if debt reaches 200% of GDP? 500%? What kind of interest rate may be required to issue more of it - and issuing more of it is necessary to repay old ones? It may keep debt escalating at a rate that might seem silly and cause an avalanche effect whereas issuing more debt requires paying a higher and higher interest rate - and that interest will cause the debt to self-escalate - in a runaway cycle where process has to end in a year or two with inevitable default. Only good thing about it is that many other countries will arrive to that point sooner thus keeping U.S. in advantageous position still.