Cultures differ in the strength of social norms and the degree to which deviance from social norms are punished. Tight cultures have strict social norms and low tolerance for deviance. In comparison, loose cultures have less rigid social norms and greater lenience towards norm violations. Tightness–looseness varies across U.S. states and these variations are related to prejudice. The American = White effect, where ethnic minorities are implicitly excluded from the American identity, has been largely documented, but little is known about the sociocultural factors that may account for this effect. The current research tested whether state-level tightness–looseness predicts people’s implicit association between being White and the American identity. IAT scores were analyzed using multilevel modeling with participant demographics as Level 1 predictors and state indicators as Level 2 predictors. Across both IATs, stronger implicit associations between being White and the American identity were observed in tighter—rather than looser—states. When controlling for additional state-level variables (i.e., proportions of Asian or Native Americans, political orientation, and openness to experience), the effect of tightness–looseness remained significant. The Asian- European American identity task yielded a significant cross-level interaction such that the effect of tightness–looseness was stronger for Asian participants than for White participants. A final analysis showed no evidence that openness to experience mediated the relationship between tightness–looseness and implicit associations. Grounded in a cultural psychological approach, the current study showed that the strength of social norms and the degree to which norm deviation is punished account for peoples’ implicit associations between ethnicity and the American identity. The key finding points to the role of a state’s culture on people’s implicit understanding of what it means to be American. In particular in tight contexts, implicit associations perpetuate being White as a normative standard and imply a relative exclusion of large segments of the population.