I've worked in both countries and I noticed at least one explanation for the productivity difference that isn't mentioned in the article. If a German is at risk of missing a deadline on a project he will put in a lot of extra hours to avoid that. An American who already puts in way more hours has much less time and energy left to make up for unforeseen circumstances. So the increase in flexibility pays off by avoiding rescheduling dependent projects. Perhaps this flexibility may have other benefits too, such as that people have more time to intellectually enrich themselves in ways that benefit the company.