In broad terms, USA is largely funded by global economy. This is done by setting US$ as master currency, so in effect, America's biggest export is dollar that gets consumed by rest of the world. When Fed prints out $6T, the inflation transfers to rest of the world and little to US. The ownership of US$ allows Americans to buy expensive goods manufactured by labor and materials in rest of the world by merely manufacturing currency as primary export.

I think it is possible that in future, Americans don't have to work and rely completely on their export of US$ as world currency. The global currency must be protected military might and a constitution that allows for fairness, justice and ability to challenge authority. This is necessary for the trust and stability in global economics. The country owning the global currency would also need to setup military restrictions so that other countries may not be allowed to match military power. All this might look bad but it is truly an economic service that is needed to be provided by someone. US citizens job is then to protect constitution, military powers and the currency. For that job, they get goods and services from rest of the world. As merely 5% of population is engaged in providing this economic service, it is probably not an inefficient either.