Staying at home substantially reduces the spread of COVID-19. Moreover, understanding why people stayed at home by addressing its social cognitive determinants can help create more effective communication to change behaviors. This study analyzed this outcome through an extended model of the theory of planned behavior based on risk perception and personal norms in four countries: the United States, Japan, Brazil, and Taiwan. 1,196 individuals participated in this study through a questionnaire focused on planned behavior, moral norms, and risk perception. The data showed that intention and perceived behavioral control influenced behavior significantly, while attitude, injunctive norms, perceived behavioral control, personal norms, and risk perception influenced intention. With multigroup analysis and ANOVA, we verified significant differences in the estimates and mean scores across cultures, revealing the need for scholars to analyze outcomes based on geography and local political culture. Given that health communications played a key role in managing the pandemic, this study clarifies the social cognitive determinants of staying at home and how the local political culture can impact their influence. Thus, we provide an evidence-based prescription for focused communications.