The United States is basically a global empire whose strategic thinking revolves around control and power. However, this is coming to an end. A global financial crisis will soon engulf the US and its current budget woes will pale in comparison to what is yet to come. This will cascade worldwide and cause the US Dollar to rapidly lose its world reserve currency status. Although this will cause extreme worldwide economic pain, the ultimate outcome will be much of the loss of American political and military influence outside of North America. Future Chinese historians will look back at this time and consider the Americans a modern day form of foreign barbarians.
Let's hope the transition isn't too violent. There is a very real threat that Americans will launch wars to prevent certain oil producing countries from switching the oil trade from US Dollars to another reserve currency. The Petro Dollar is after all the last bulmark against total US Dollar collapse.