This omnipresence of the USD has always been key for the US economy, as it has allowed for the US to issue more and more debt at quite low prices independently of the markets situation. The perceived-risk of the US debt had always been very low (notice the past tense here). The US government of course knew this, and used it on its favor but they have been using the strategy for too long and too hard. As it happens with everything, if you overuse and stress something for long enough, it breaks...
| EUR-USD exchange rate. Credit: Yahoo! |