Europe does not have the same market conditions as the US. The continent is divided into a gazillion amount of small countries, each with their own rules, laws, regulations, languages, customers, pension systems, healthcare systems, and taxes. Even the currency is not the same everywhere. Not to mention the cultural differences.
One thing they have for them is a lot of money to invest from their American market, and enough momentum that they can afford barely sustainable European operations for a few years whilst they figure things out and streamline everything.
EU federalism would solve this issue, and likely cause others.
The concept of European federalism is extremely interesting to me. The first I heard about it was at a house party in Prague, from a group of very excited young people. It feels both impossible and inevitable.
Pretty hard economy to survive in.