I have often heard it said, most recently by congressman and presidential candidate Ron Paul, that the US should not be the policeman of the world. That is just conventional nonsense. It is a platitude people say because they've heard it and not heard it contradicted. A moment's thought shows how preposterously wrong it is. Our cities are often plenty dangerous with policemen. Imagine urban life without them.
That is what the life of nations would be like were it not for a world policeman.
Except for Antarctica and the oceans, the whole surface of the earth is under some government or other. And every one of those governments at least in theory attempts to suppress crime and other anti-social behavior. But among the governments themselves there is no government, no one to suppress crime and anti-social behavior of governments. History has shown that governments have been the worst malefactors, committing crimes and monstrosities that reduce the worst efforts of the Tony Sopranos and street corner muggers of the world to insignificance by comparison.
To deal with this lack of a world order there are only the US and the UN. The UN is more than just useless - it is part of the problem. That leaves the US. Without the US there would be even more anarchy and violence than there is now.
And please don't reply by claiming that the US is responsible for most of the violence. That is just fatuous and not worth your saying or my replying.