The US debt/gdp is slowly growing and sits currently at 100%. What about when it hits 120% like Italy or 180% like Greece? Regardless of whether people have jobs/money if there are no buyers of US bonds, this leaves the Fed no choice but to buy them or the govt has to slash spending. The monetisation of deficits caused some of the hyperinflations in the 20th century (eg Bolivia, Yugoslavia).
"Why would the Americans let their currency hyper inflate?"
They may not have any choice. The major costs of the US budget are the medicare/social security, military, and interest. If they cut medicare and other social programs they risk being voted out of office. The recent automatic $1.1tril spending cuts are a joke, $100bil over ten years when the deficit is 1.5trill and growing. There's also a real lack of political will to fix the problem, instead the Repubs & Dems just argue.
