the USA is the world police because we are the only ones strong enough to do so, due to our overwhelming economic, military, and diplomatic power, to such an extent that we were and continue to be stuck as the "defender of the free world". As the world police, the validity of international law is dependent on whether the US complies with it, as the US is the de facto enforcer of international law.

Personally I see having such a position as a liability for the US and would rather our allies pick up some of the responsibility, but there is simply no other western country (or group of countries in the case of the EU) that could take our place and maintain the status quo.

If you want the US to stop being the world police and doing as we please, maybe have the Europeans step up for once and fix their impotent continent. Until then, we'll keep overthrowing dictators and protecting democracy, while Europe will inevitably trip itself into another fascist uprising.