Productivity is a measure of output for a given workforce, not working time. Japan's problem isn't one of people surfing the web at work, it's arcane hierarchical structures getting in the way of getting things done.
That's a very optimistic view of american "productivity" based on anecdotal evidence. The reality is that while there are a few places where american workers are actually rewarded for getting things done, most of them are rewarded based on time worked.
Most software shops I've worked in have been spending the vast majority of their workers' time on servicing technical debt, while promoting the people whose primary contribution was that debt.