The US has not pegged their currency. They've made other currency policy decisions under the hope that the US currency can handle the debasement (and so far they have proven true).
Remember that when you short a currency, you also are taking a position about all the other currencies in the world. So rather than say you don't like US dollars you need to say, I prefer X to US dollars and think they aren't currently trading at the right ratio (and if you are shorting you have to account for a very expensive transaction cost).
So rather than asking what the play against the US dollar is, ask which currency you prefer. The international markets do this everyday and so far they haven't found a very compelling alternative.
You can be right about the problem, but being able to enter and exit a market to benefit from such prescience requires a lot of timing. If the wreck is slow motion, you can lost most of the utility of your insight by transaction fees, interest, and the contrarian, emotional whims of the market you play in. It's better to have other peoples' money at your disposal. Hedge fund managers are in a great spot.