A couple of sources peg global governmental military spending at $900 billion to $1 trillion in 2005 (these sources are the CIA World Fact Book and the Stockholm International Peace Research Institute, which relied upon by European governments for its data). Of this total, the U.S. is responsible for more than half of the total, or around $500 billion. Per year. That's 10 times Russia, over 10 times China, 2 times the entire European Union, etc. Now I know that sounds like a lot, but to put it in perspective, it's less than 3 times the market cap of Google, and about 20% more than the market cap of Exxon Mobil.
Do you ever wonder what would happen if we just stopped? Stopped policing the world, protecting it from...itself? Consider Iraq: all sorts of bad things were (and maybe still are) going on there with respect to terrorist hideouts/safe places/weapons development. Now we're there. But what about its neighbors, Syria and Iran? Aren't they terrorist states? So don't terrorists have free reign there? Yet in practice, both are democracies with elected officials who worry about losing their jobs if they don't please their constituencies. And neither of them are attacking our borders. Iran's oil flows freely and suffers no sabotage attacks; Iraq's barely flows at all and suffers greatly from sabotage. I'm sure Iraqi citizens as a whole feel safer with us there for the time being, but is that enough to justify the tremendous cost? And wouldn't the cost end exponentially more heinous, heartbreaking crimes against humanity if re-routed to civilizing at least some, if not all, of the war-ravaged sections of Africa? I don't know; I hope somebody's analyzing the facts and making the proper decisions on how to spend that half a trillion per year though.