>It does every day, though, doesn't it? How much of a currency
>devaluation has to occur before the U.S. can't service its debt? When will
>the US government start being unable to write the checks?
It's not the government that has a problem: the foreign capital inflow has effectively been financing a marginal propensity to consume of over 100% throughout this expansion, and, more recently, (corporate investment + stock retirements) > cashflow. While a reversal of the inflow wouldn't mean the onset of Armageddon, it could involve loud crunching sounds.
Doug