I'm not either, but as I understand it, it has a lot to do with their paying back their debts and the interest rate they must pay. I know that the official inflation rate has to do with the interest they pay as well. I'm not 100% sure how all these tie together though.
The US may use low inflation to reduce their defecit exposure: It may be part of the American political pretense unfolding (Kabuki Dance)
The value given to currency is based financial perception, demand and latitude of influence. Currency has no collateral; the gold standard limited the volume of US currency in circulation. Today there is approximately 16.8T dollars in circulation. There is not enough gold in this earth to collateralize 16.8T.
Low inflation, and “trust” on US securities as a solid place to park cash allows for the dollars to retain it's “perceived” value. It's also the world's currency where the most expensive commodity it valued at; Oil.
Quantitative easing by the feds is creating not only an artificial demand for US Treasuries by buying & selling short/long yield Treasuries, and by proxy creating a low interest environment, normally associated with a robust economy. That could change rapidly if the US financial cliff is not resolved in January 2013. The Chinese already have reduced their US treasury exposure considerably in the last year.
A global domino effect to follow, and the dollar will take huge hit, the Arabs, and future speculators in Oil will be pissed off: Oil is valued in dollars.
Republican intransigence on raising taxes defies logic; why create uncertainty. Perception is reality and essential for financial markets to function on virtual wealth.
They haggling over a trilllion in revenues over 10 years creating uncertanty. If the stock market over-reacts we could see a few trillion dollars of market capital value evaporate in weeks. Fight for a trillion, only to see 3T of capital wealth evaporate in stocks, bonds, commodities, derivatives value.
For all we know, this may all be a concerted ploy to create a US financial “crisis”. Lunatics are running the US goverment. Currency markets will devalue the dollar, due to it's high exposure, in turn a devalued dollar will reduce the deficit in two ways: Interest payments with devalued dollars & US treasuries, when re-deeming at maturity, will have a value lower than when originally invested in.
Que Sera Sera