For this reason I think such a study should be focused on Europe and compare the countries there with each other, to see if this theory is a good one or not. I

For this reason I think such a study should be focused on Europe and compare the countries there with each other, to see if this theory is a good one or not. I don't think it makes much sense to compare it to US, because there are other factors contributing greatly to the success of US entrepreneurs and it has nothing to do with "being more risk-averse or not". It has to do with the fact that the US is actually a huge single market. EU really isn't right now. It's not easy to just launch a company in a country and easily have success in another. Certainly nowhere as easy as it is to launch an online business in one state in US and have success in other states. There are other factors, such as concentrating many entrepreneurs in one place, which also leads to a concentration of investors in one place (talking about Silicon Valley here). There's also a huge concentration of media in the US that is followed by other countries as well. How many European media sites or blogs do you know? I bet you can count them on one hand. It's much harder for a company in Europe to get promoted across all European countries, let alone to have Americans hear about it. I'm sure there are many other factors as well that make the US a much easier startup environment than Europe.