Think about it, if it collapses, hundrends of millions people around the world will lose their jobs exporting to the US market, trillion dollors deposited in US banks and treasury will suddenly disappear, investment and credit will dry up, governments everywhere will be in crisis when their people become hungry and angry as these crisis happen, the world will become chaotic place as countries attacking each other and no one has the authority to keep order. That's why the world gives the USA, and only USA, the power to print as much money as it needs to get out of any trouble it has