Fighting the COVID-19 pandemic requires large numbers of citizens to adopt disease-preventive practices. We contend that national identification can mobilize and motivate people to engage in preventive behaviors to protect the collective, which in return would heighten national identification further. To test these reciprocal links, we conducted studies in two countries with diverse national tactics toward curbing the pandemic: (1) a two-wave longitudinal survey in China (Study 1, N = 1200), where a national goal to fight COVID-19 was clearly set, and (2) a five-wave longitudinal survey in the United States (Study 2, N = 1001), where the national leader, President Trump, rejected the severity of COVID-19 in its early stage. Results revealed that national identification was associated with an increase in disease-preventive behaviors in both countries in general. However, higher national identification was associated with greater trust in Trump's administration among politically conservative American participants, which then was associated with slower adoption of preventive behaviors. The reciprocal effect of disease-preventive behaviors on national identification was observed only in China. Overall, our findings suggest that although national identification may serve as a protective factor in curbing the pandemic, this beneficial effect was reduced in some political contexts.