If a startup wants to reach a similar customer base as a startup in the US it will always have to deal with 50 different markets with 50 different legal systems, 50 different marketing channels, and 50 different social networks. Starting a complete web-based company like Spotify or Soundcloud may still be possible because itunes has paved the way to organize media rights efficiently, but as soon as you touch the bricks and mortar world it becomes a different story. The startups I know were first of all focused on their home country and became international only much later, after building local representations in the different countries, and then they had to deal with the local competitors and became successful in only a subset of these countries.