The EU isn't really a single market. While Amazon.com, Yahoo, Google, MS and others were able to start with a single product or service for the entire country, they each have many multiple offerings in various EU countries.
You can't just make a quality OS or a website in English and start selling all over Europe. You can do that in the US and be a market leader in every state.
That's not actually true. It's [arguably] a single market, but it's not a single currency - large parts of the EU do not use the Euro (Britain, Sweden, Denmark and all of the newer entrants to name a few - it's only I use by 16 of the 27 member states).
You can't just make a quality OS or a website in English and start selling all over Europe. You can do that in the US and be a market leader in every state.