Theories of democratic diffusion predict that exposure to liberal democracies fosters support for political liberalism, while recent studies on Chinese overseas students suggest studying abroad generates backlash against liberal values. Using a unique four-year longitudinal dataset of nearly 1,000 Chinese college students in China and the United States, we examine how studying abroad shapes studentsâ ideology, attitudes, and identity. Our findings challenge both perspectives. Students who study in the United States are already more politically liberal, market-oriented, and cosmopolitan, and less nationalistic than their peers upon departure, underscoring the importance of selection. Ideological preferences remain remarkably stable throughout college, regardless of location. However, support for Chinaâs political system and affective identification with Chinese national identity declines among students in both countries from 2022 to 2023, with a greater decline among students in the United States. These results show that selection, home-country shocks, and host-country context jointly shape overseas studentsâ political attitudes.