A growing body of research argues that external threats from the international system strengthen ethnocentrism and authoritarianism, personal values anchored in national identity. We evaluate a necessary implication of this argument, that threat-driven value change manifests in broader social behaviors. Specifically, we analyze revealed value change in a non-political setting: American consumers' choice of supermarket brands that symbolize national identity. Our empirical analyses leverage US counties' quasi-random exposure to US Iraq War casualties to identify the effects of local casualties on the weekly market share growth of ``American" supermarket brands. Using weekly supermarket scanner data for a representative sample of over 1,100 US supermarkets and 8,000 brands, we find that the weekly market share of American brands grew in fallen soldiers' US hometowns. Variation in share growth across store demographics is consistent with the external threat mechanism. We rule out several alternative mechanisms including partisan cues, other product characteristics of American brands, and animosity towards other countries. These findings strengthen IR's theoretical microfoundations by showing that international politics reshapes values enough to change broader social behavior.