The most likely cultural trait 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 tendency in the U.S. to value longer working hours and productivity as part of a capitalist economy, while the Netherlands is known for its emphasis on work-life balance and social welfare, resulting in shorter workweeks.