US debt will not be paid off. It can't be paid off. NO AMOUNT of taxation, reasonable or otherwise, can put a dent in the US's ocean of debt.
That means a DEFAULT, an overnight trashing of the dollar's value (20-30% inflation in less than a year, it happened to the UK in 1975), large increases in gas and food price, and widespread unemployment of perhaps 30%.
Oh, and world reserve currency status? Say goodbye to it. That will be a killer blow to the USD.
A good argument, with only one minor issue... why would the US need to pay the debt off in the first place, and how would this lead to a default? US national debt is actually relatively
small as a percentage of GDP right now, both compared to historic levels and to other countries. The only thing putting them in any danger of defaulting whatsoever in the imminent future is the Republican's assholish refusal to increase the debt ceiling, and even that's incredibly unlikely to happen.