That's not true. We don't need the US to lead. The natural state of human social equilibrium in anarchy, and was indeed the mode of social equilibrium in most of human history until the "tragedy" of agriculture.
And indeed, if you take any half decent IR class they will teach you that the state of international relations is anarchy.
Killing lots of innocent people in lots of places for no discernible reason would only be "leadership" if one thereby inspired others to do the same thing. Fortunately that hasn't happened yet...
And indeed, if you take any half decent IR class they will teach you that the state of international relations is anarchy.