These graphs are irrelevant, they barely show how much money these people make for the time that they work. You can't really compare the amount of money Americans vs the Chinese (per capita) make, can you? Do you really believe that it shows how much work a person does? I mean, I'm surprised that you've just used that as your argument. It's not that companies build their factories in countries like China, Thailand or even Poland or Slovakia for no reason. It's because people work more BUT the labor cost is lower. Isn't this obvious?
If it comes to the culture it's what Pittsey said plus what I mentioned - Americans know how to work for their money.
I work in an international (American) company with Americans and with Asians and no way in hell I'd ever accept that Americans work harder than the Japanese or Chinese. I've studied with Americans and the Japanese and again, same story. Actually it has been one of my main observations that the Japanese and Chinese are hardcore workers. Americans never work a lot where I'm at but they're always down to business, where the money's at.
I've met a girl that had worked in a Chinese factory. 15 hours a day, 6 days a week and worked on Sundays too but "as a hobby". They had 15 minute breakf every 4 hours. Other than that they weren't allowed to sit down - pretty hardcore work.
She used to see her family once a few years and wouldn't go outside at all. She said that it's pretty normal. She worked hard, yet didn't make much money. It's what happens to millions of the Chinese. That's how you get your shoes and why the CEO of Nike gets paid more than the whole Chinese factory combined. Does he work harder than 10 thousand Chinese people from a factory manufacturing those shoes?
I didn't even mention Poland but since we're studying this example I can speak for my country. It's more about Polish companies, especially public that make people do unproductive things. It's often hard work but not always necessary work. We have public administration and dying public companies where people work long hours and do hardcore but rather pointless work. Because the top management sucks, because of corruption, because the government is silly etc.
But on another hand seeing someone work as hard as some Poles do who really work for a reasonable goal is a rare sight. They earn funny money here, they move abroad where jobs are easier and pay far more, and most foreigners I've met that had Polish workers usually said great things about them. Usually the laziest bums move abroad - to Germany, England, the Netherlands (recently) and anyway they're said to be great workers compared to "lazy locals", then those locals complain that they're taking all the jobs.
Also I don't want to sound like an asshole but my university thesis on one of my majors is about the differences between Japan and the western world concerning project management in those countries. The Japanese simply work much harder. It's in their culture.