You're assuming the necessity of a great, essentially imperialistic power in the world. The source of the scathing criticisms you will often see coming from outside of the United States is the observation that misery was visited by some alien source.
There's no doubt that villains abound .. the question is, does the world need a "global policeman"? The historical record shows that these powers, even when acting with the best intentions, usually lengthen suffering where they intervene by distorting local and regional power dynamics. And more often than not, the motives for selecting a given site at which to intervene are less than scrupulous (Britain in India, US in Iraq) or are perpendicular to the host's interests (Vietnam), in which case there is no excuse for the resulting fallout.
There's no doubt that villains abound .. the question is, does the world need a "global policeman"? The historical record shows that these powers, even when acting with the best intentions, usually lengthen suffering where they intervene by distorting local and regional power dynamics. And more often than not, the motives for selecting a given site at which to intervene are less than scrupulous (Britain in India, US in Iraq) or are perpendicular to the host's interests (Vietnam), in which case there is no excuse for the resulting fallout.