I was comparing the US and the EU because of a similar size. When you have 160 parties representing the views of 500 Million Europeans, it is very unlikely that having merely 2 parties representing the views of 300 million Americans is a natural, healthy state of affairs. The EU is of course not a role model for democracy, but it shows that the lack of diversity in US politics can not be a natural outcome of US voting habits. The lack of diversity (and thus lack of democracy) is fully intentional.