Despite all of the economic hand-wringing in the US, people throughout the world believe that the United States is where to place their trust. They are literally putting their money where their mouths are. Just look at this milk carton. Missing: $1.5trillion in $100 denominated US paper currency. https://video.foxbusiness.com/v/6116577107001/#sp=show-clips
It's sad that every other major currency in the world is less trustworthy than the US. The Euro was supposed to hold great promise of stability, and initially did, but then look what they did over the last couple of years.