My impression at a state university in the US was that CS was one of the least demanding majors in terms of time spent on coursework outside of class. Sadly I do not have any data about this.
CS was likely the most demanding major at my university in terms of workload outside of class. Depended on what classes you took, but the toughest demanded ~30hrs per week of problem sets + coding assignments each. Made being a D1 athlete in a top national program very tough to pull off.