1) USD is worth something not because the US gov says so, but because China says so. The day China says that USD isn't worth anything, the USD will collapse.
That is a fundamental misunderstanding among the tinfoil hat crowd on this site.
USD is worth something because ultimately it's backed by an army that can insist you pay your property tax in USD, and because it's backed by the outflow of payments from the US government, which only pays its people and contractors in USD.
No, the US domestic economy alone is not enough to keep the dollar valued where it is. The government is insolvent, we all know that, and the economy consistently runs a trade deficit. The US dollar keeps its value because it is de-facto world reserve currency and has been for decades. When the rest of the world loses faith, the US *cannot* keep printing, nor can they maintain ZIRP, without huge devaluation of the dollar and subsequent hyperinflation.