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 is reflected in the emphasis on work and productivity in U.S. culture compared to the Netherlands, where there is a stronger focus on work-life balance, health, and social welfare policies that support shorter workweeks.