Why do people behave differently in different countries?

Behaviour is a result of your environment groing up. Lots of things have an impact on the way you behave, such as:

Parents
School
Social status
Friends
Access to the Internet

Different countries have different customs. For example (and this is not an attempt at stupid rudness) european parents care more about the education of their kids than american parents do (does not imply specifically, but more generally). In Europe your kids are the most important thing in your life, and you would easily sacrifize your life if it meant that your child would live on.

The general idea in Europe (or at least my idea) is that America has a lot of great ideas. I love your system of "as little government control as possible", but you have to understand, that the notion of complete freedom has its consequenses. I may have made a few spelling-mistakes in this post, but over-all my english (as a 2. language) is way better than that of an average american.