Who ever said we have to pay back our debts? The question is how long will the world agree that the dollar has value? Why are they no longer buying our debt. The last figure I heard was that the Fed was purchasing 70% of the new US debt. China is slowly selling off her US Treasuries. Does that suggest that she has confidence in the dollar?  Does it really show that "we all agree" that the dollar has value? I don't think so.
China has also reached swap agreements with many other countries and so have other countries reached swap agreements with each other to avoid using the dollar in bi-lateral trade. China has also set up a CHIPS system for clearing currency to compete with the US SWIFT system. There are lots of things going on that are enabling many of our trading partners to conduct business without the dollar. Why are the doing this? Why are they doing it now? Why not 20 years ago? You don't suppose it could signal a loss of confidence in the dollar do you?
		
		
	 
As usual, you have the cart before the horse. 
One of the major policies right now is to try to get money flowing in the economy by making the return on US Treasury bonds (which are very safe) low, so that the returns on (relatively) more risky investment in the larger economy becomes attractive.
People not buying US Government bonds is a feature of the current policy, not a bug. 
Whether nations with currencies other then the US$ use dollars for trade or not is completely irrelevant to the value of, or confidence in, the US$. It is a technique for making the sums nice and easy; it is becoming less relevant as transfers become more automated. 20 years ago, physical payment had to travel from one country to another, with inevitable delays that could lead to problems for contracts denominated in multiple currencies; so the US$ was a convenient stable 'peg' to hang such trades upon. Electronic transfers happen fast enough for this to be irrelevant. 
The changes don't signal a loss of confidence in the dollar; just a rise in confidence in modern electronic banking systems. They may seem 'old hat' to you, but to large swathes of the world, trusting computers rather than physical pieces of paper is a very new idea.