(May 8, 2010) It's 2154, and American Terrorism has been totally privatized. In fact, it has become the undisputed enforcement arm of the criminal plutocracy on Planet Earth. In other words, the future is just like today -- except the terrorists have gone off-planet and expanded their field of prey.
In Avatar, the plutocracy of Planet Earth needs more resources, so American ex-military mercenaries are sent to rape-and-pillage a planet called Pandora for its so-called "unobtainium."
By the way, "unobtainium" is a Real World term for valuable rare-earth metals like neodymium, terbium, dysprosium, lanthanum, yttrium and thulium. They are currently used for weapons, as well as digital cameras, computers, Priuses, and iPhones.
In fact, according to the UK's Daily Mail, industries that rely on "unobtainium" are estimated to be worth an astonishing 3 trillion pounds (US$4.5 trillion), or 5% of global GDP. Thus, wars and invasions of other planets are completely plausible as a possible Real World future scenario.