The practice of diplomacy has changed dramatically in recent decades as a result of technological advancements and shifting geopolitical concerns. No longer confined to the cloaked and closed-door practices of elite state institutions, the diplomatic landscape has broadened, and been made visible, across space and scale. Amidst this rapidly changing environment, it is imperative to understand how states are adjusting their material diplomatic infrastructure and what that means for everyday diplomatic practices. While many countries have adjusted to twenty-first century diplomatic realities by adapting to a more mobile, maneuverable diplomatic corps and fewer facilities, the United States remains committed to a widespread diplomatic network, the largest in the world. This diplomatic footprint is the hallmark of universality, a sustained effort over time to acquire near total diplomatic coverage by dotting the world with embassies and consulates designed to look, work, and behave in a similar, if not, ageographic, manner. Attending to this understudied phenomenon means studying the historical and geographic conditions out of which this relatively even and uniform diplomatic apparatus materialized. It further means analyzing the contemporary pattern of U.S. diplomatic infrastructure against the shifting terrain of diplomatic norms and space. Drawing empirically on interviews with elite diplomatic practitioners, substantial archival material, and the researcher’s own experience working within the U.S. diplomatic assemblage, this study has sought to examine why the United States remains committed to universality and what embassies and consulates actually do to secure U.S. foreign policy goals. Specifically, the study—presented in this dissertation as three discrete original research articles—is framed by the following research questions: (1) What ideas and policies shaped the geographical footprint of U.S. diplomatic infrastructure over the course of the twentieth century? (2) How does the globe-girdling U.S. diplomatic assemblage reflect and influence geopolitical ideas and practices? (3) How does the grouping of diplomatic missions along regional lines reflect and influence U.S. foreign policy?