The premise that underlies the prescient initiative of our two editors is that the United States, as the sole superpower in the post–Cold War era, is likely to play a preponderant role in the evolution of contemporary international law. Understanding the particular role of the United States is indeed crucial for students of contemporary international law and politics. I nonetheless argue that in the fundamental regime of customary law the assumption of preponderant influence is unwarranted. The United States is materially more powerful than any state has ever been. However, for reasons related to the complex identity of the United States, and to changes in our understanding of the creation and operation of customary international law, the United States is currently less influential in the elaboration of customary legal norms than is often presumed.