Previous research suggests that White US Americans associate being American with being White. In six studies, we followed up on this research in the context of acculturation. We hypothesized that White Americans would have a phenotypically white representation of immigrants who adopt mainstream US American culture and a stereotypical representation of those who maintain their heritage culture. At the same time, we hypothesized that White US Americans would expect immigrants with light skin to be more likely to assimilate and immigrants with dark skin to be more likely to separate. Our results generally supported these predictions. Using reverse-correlation designs, the first two studies showed that White Americans had a white-looking mental representation of Asian and Arab immigrants who adopted US mainstream culture via acculturation or by holding a common or dual identity. By contrast, participants had stereotypical mental representations of these immigrants when they maintained their heritage culture. Two follow-up studies showed that these perceptual processes made immigrants who adopted US mainstream American culture less likely to be racially profiled but also less likely to be regarded as qualified for integration support programs. In the last two studies, we subtly manipulated the skin color of a set of pictures of individuals described to be South American immigrants. Participants found lighter skin color to fit better and darker skin to fit worse with adoption of US mainstream culture. Moreover, when skin color was manipulated to look lighter, immigrants were seen as more likely to assimilate, which in turn decreased the degree to which they were perceived as threatening. Together, these findings highlight the interplay of phenotypical characteristics of immigrants and acculturation expectations of majority-group members.