Now that the US dollar has slipped to new lows (US$2.00 a £, US$1.50 a €, US$1.00 a C$, US$0.01 a ¥, US$1.00 a Sfr), now that the US has been dissaving for several years and does not seem to reverse course soon, one can be worried was lies in the future. But there is hope.
Take the research of Pierre-Olivier Gourinchas and Hélène Rey, who show that the US is helped in two ways: 1) by its particular position within the international financial system, which allows it to benefit from a significant interest premium, 2) by the structure of US debts and credits, which allow to earn net interest despite having net debt (NBER 11563). They claim also that 31% of necessary external adjustments come "automatically" from such valuation effects (NBER 11155). In fact, there is remarkable stability in the system (NBER 11996).
The future is not so gloomy after all.