Background The purpose of this study was to clarify the structure of subjective well-being in post-COVID-19 and to provide baseline information for future studies. To this end, we clarified the structure of subjective well-being (SWB) based on psychological factors that affect SWB. The Japanese and English versions of the scale were developed, and the scale and the SWB were also used to determine the cultural characteristics of the Japanese and U.S. participants. Methods and Results In Study 1, we administered a questionnaire to 1721 participants in Japan (aged 20–79 years). A total of 107 psychological factors that were shown to influence SWB in previous studies were selected, and factor analysis was conducted on items that showed an association with SWB. The results revealed four relevant factors: 1) Accepting what is, 2) Grateful for connections, 3) Ikigai/Life fulfillment, and 4) Love for self. In Study 2, we developed Japanese and English versions of the four-factor well-being scale that was clarified in Study 1 and administered them to participants in Japan and the U.S. In Study 3, we identified comparative cultural trends in SWB and the four-factor well-being in Japan and the U.S. (Japan: n = 2628; U.S.: n = 2617). Conclusions This novel study is the first cohort study to capture the characteristics of contemporary SWB during the COVID-19 pandemic. Through this study, we provide a new perspective on the structural elements of SWB in people living today.