The U.S. dollar, first and foremost, is linked to energy costs. Oil is denominated in dollars, until it isn't. Currently, the U.S. has cheap domestic sources of oil and gas, thanks to the shale oil boom which will last anywhere from another year or two to another thirty years, depending on who you believe. China has a huge trade imbalance with the US, holds a significant portion of the US debt through treasuries, and has an export-driven economy that would grind to a halt if it de-coupled from the US. Pretty simple case of dependency.