As long as the Fed lets banks materialize money out of thin air for 2% to loan out to someone else, there will be someone willing to loan the US money for 2%+ε.

As long as the Fed lets banks materialize money out of thin air for 2% to loan out to someone else, there will be someone willing to loan the US money for 2%+ε. The deciding factor is not whether or not the US can borrow money, it's whether you can buy anything outside of the country with that money.