The cultural trait most likely responsible for the difference in workweek length between the U.S. and the Netherlands in 2020 is:
**The U.S. culture prioritizes capitalism, while the Netherlands’ culture prioritizes health and welfare.**
This response reflects the broader societal values and priorities that influence work-life balance, with the U.S. often emphasizing work and productivity, while the Netherlands tends to emphasize social welfare and health, which can lead to shorter workweeks.