This dissertation attempts to provide an understanding of the widespread anxiety, vigilantism, suppression of dissent, and violation of civil liberties that took place in the United States from 1917 to 1919 and argues that it can be found in some Americans' understanding of and reaction to racially-charged propaganda. As the United States inched toward war with Germany in 1915 and after declaring war in April 1917, many propagandists began referencing the allegedly inherent characteristics of Germans as evidence of German American disloyalty and the existence of a vast "Pan-German" plot to undercut or even destroy American democracy. The imagined conspiracy grew to encompass most of the fears that had plagued the Anglo Saxon middle-class since the 1870s -- immigrant radicalism, race suicide, the capability of "racially inferior" immigrants to assimilate and self-govern, and the continued deference of African Americans. To many anxious Americans, Germany and German Americans became a very real entity to which these long-held fears could be transferred. American propaganda produced during the First World War, though, was not a cynical ploy to fool the American people into supporting intervention on the side of the Allies. Leading Americans-- politicians, editors, and social elites-- were convinced that a global German conspiracy threatened the security of the United States and hoped to enlist the American people in staving off the existential threat they believed racially degenerate Germany allegedly posed. This dissertation paints a unique picture of the United States in the Progressive Era and contributes to literature on the history of emotions, race/ethnicity, progressivism, American culture, war's impact on society, and the First World War in general.