Since the drafting of the U.S. Constitution in 1787, the document has served as a model for constitutional design for many other democratic polities. Core elements of U.S. constitutionalism, including adoption of a written constitution, entrenched and judicially enforceable human rights, and federalism, have become commonplace in other nations’ constitutions. One key element of U.S. constitutional structure, however, has failed to find a receptive audience abroad: the separation of legislative and executive powers. Most modern democracies have broken with the British model of parliamentary supremacy in favor of some system of judicial enforcement of entrenched human rights, but nevertheless have retained the British practice of selecting the heads of executive branch agencies from within the ranks of the legislature. This Article explores the U.S. commitment to separating and dividing legislative and executive powers, and posits cultural pluralism as a key reason for this structural commitment. In addition, it suggests that creating a political check on the legislative process provides an additional normative reason for embracing the practice. In the end, U.S. separation of powers doctrine reflects the distinctive nature of the polity: in a cultural jambalaya, citizens have good cause to be suspicious of the government and its motives, and hence to establish structural safeguards against the perceived risk of tyranny.