It could have a signifcant role but I don't think it would be enough at such time. Besides such on going debt isn't look like a normal one, though we can earn million dollars here that doesn't mean it can fit to a much more vital concern. And the US government are working with their debt much more complicated than just replacing bitcoin as a payment for their own debt. It just doesn't work that way, and I bet that the US government doesn't get bothered to even think about it as a solution.