If the US really ran out of resources, I wouldn't count it out. In the mean time, it's more like we prop up dictators who agree to sell oil exclusively in our currency (see Saudi Arabia) and invade every country small enough to push around that tries to sell oil in anything but US dollars (see Saddam being in talks with France, or Gaddafi planning to sell oil in the gold dinar). Since the whole world has to buy oil, the whole world has to have dollars. Then we print more US dollars, devaluing the existing US dollars in global circulation and effectively stealing wealth from the rest of the world for the benefit of our banking system. Yeah, we also give sweet contracts to Haliburton so that they can pillage third-world oil fields in the middle of our wars and there is some immediate benefit from that as well, but I'm betting that propping up the petrodollar is the most important way that we're leveraging the military for economic ends.
Sure. But ultimately, debt is meaningless unless collected. In a scenario of global economic collapse, anyone who wants to collect their debt (if it even means anything anymore) from the US would have to go through the US military first.
