On a quick note...I would have to say that the laws of the US provide a unique and time-tested opportunity for startups. This has driven the US to become a destination for many of the world's immigrants, leaving their own countries less populated with potential risk takers.
The notion of a free market is what distinguished the US from its European counterparts at its inception and has since demonstrated the ability to learn and grow. The benefit of the US at that time was a clean slate economy without all of the potential 'baggage' that the European countries possessed in the monarchical systems. What's more, for the most part it didn't matter where you came from or who your family was in the US. All that mattered was market potential.
Though European countries have moved their economies in much the same direction they still have to contend with the history of their governments. Culture and history are slow to let go of a people group. New ideas take time to be successfully introduced on an indigenous level if they are to become part of the cultural paradigm and identified history.