It's the same reason the police can carry guns and non-police are more restricted. We trust the police. If the police wanted to, they could go berserk and do tons of damage, given their training and armament, but they generally don't do that. And having guns is a necessary part of being policemen; force to counter force. The US, like it or not, is like the police of the world. Or was, back when other countries trusted us. I think we still do have a large measure of trust, albeit not as much as before. When North Korea, which is a country where apparently the leaders have no problem with having massive amounts of people in the country die on a regular basis, gets nuclear weapons, people are afraid. The allies of the US aren't afraid of the US because they know we're not going to lob a missile into the middle of Britain tomorrow. With North Korea or Iran, we don't know that.

[qq=Glendon] Sadly, the "War on Terrorism" is not winnable with our current strategy. Much like the War on Drugs, it is doomed to fail.[/qq]

Depends on your definition of "win". Winning can mean "reducing as much as possible". A war on any crime will fail, in the sense that crime will still exist to some degree. We still have theft, rape, and murder, on a daily basis. That doesn't mean we should give up fighting thieves and rapists and murderers.

[qq]America has the most overwhelmingly powerful, advanced, and destructive military in the world. Too bad that means precisely jack against this enemy.[/qq]

Our military strength could defeat this enemy. We could lay waste to the entire country; we have the strength to do that, if you could call it strength. Our values are what are going to defeat us, not our lack of strength. Historically, I think we are acting very strange, in NOT laying waste to the entire country. Historically that's what countries do in war. I think in this case, fighting this war as a WAR probably couldn't be justified, so we're only half-fighting it.