Good post by Barry Eichengreen, Professor of Economics and Political Science at Berkeley, on the potential impacts to the US if dollar premium is lost.
It is difficult to estimate the cost to the US of losing the dollar’s position as the leading international currency. But 2% of GDP, or one year’s worth of economic growth, is not an unreasonable guess. With foreign central banks and international investors shunning dollars, the US Treasury would have to pay more to borrow, even if the debt ceiling was eventually raised. The US would also lose the insurance value of a currency that automatically strengthens when something goes wrong (whether at home or abroad).
The impact on the rest of the world would be even more calamitous. Foreign investors, too, would suffer severe losses on their holdings of US treasuries. In addition, disaffected holders of dollars would rush into other currencies, like the euro, which would appreciate sharply as a result. A significantly stronger euro is, of course, the last thing a moribund Europe needs. Consider the adverse impact on Spain, an ailing economy that is struggling to increase its exports.