In order to assess whether the United States is an empire and what we could learn from such an analysis, we embark on a dual task. We evaluate American imperial tendencies based on Michael Doyle’s criteria and then compare them to the Athenian informal empire of the fifth-century BC. In our comparison, we focus on how the Athenian empire was created and what are its commonalities with the US world order. We also explore their various differences at the level of international and domestic politics and their plausible consequences. The criteria we use are economic inequalities and military interventions and motives and national style. We suggest that the United States is a republic with imperial tendencies but not yet a Machiavellian imperial republic. Were this to happen, it would endanger the future of globalisation and the stability of the world.