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 answer reflects the differing attitudes toward work-life balance and economic structures in each country. The U.S. often emphasizes longer work hours and productivity as measures of success, while the Netherlands places a higher value on work-life balance, resulting in shorter workweeks.