This paper examines the contestation over otherness – in the form of ethnicity and national identity – that arose in the U.S. during World War I, culminating in the Red Scare of the 1920s. In the narrative of “Americanization,” immigration policies were joined with a militant nationalism, aiming to eliminate “enemies within” and from without, through a process of deportation, the criminalization of dissent and military interventionism. The demonization of immigrant-otherness became a means of strengthening solidarity among Anglo-Saxons, at a time when their cohesiveness was being challenged internally. As such, the history of America's internal control over its immigrant self is the familiar one of the limits of liberalism.