Meh, IT is much more than Facebook and Google.
Besides, those companies also have research centers in Europe.

Sweden for example has an impressive game industry for its size (e.g. DICE and Massive).

The US has the biggest home market, which makes things far easier for internet companies and in general companies which rely on brand value. In Europe there is the language and culture barrier which makes it difficult for an internet company to gain the necessary scale. Spotify and Skype are exceptions.