[wheybags]

IMO the biggest barrier is internal mobility. The European silicon valley never happened, because people don't want to move around. The biggest single barrier is language. I'm Irish, and young Irish people often emigrate (way more than in other countries). When I look at where my college classmates ended up, it's mostly America or the UK. We also emigrate a lot to Australia and New Zealand. In other words, we only really emigrate to English speaking countries.

Almost nobody goes to France, Germany, Spain, Italy, etc. The mainstays of the European economy. Let alone central or eastern Europe. But if you're a young talented engineer in the middle of nowhere usa, you can just easily move to the bay area without any issue. That cultural unity IMO is America's biggest strength, and the lack of it is Europe's biggest weakness.

Note: I've lived in Ireland, the Czech Republic, and France, so I know first hand how hard it is to move inside Europe, and I understand why people don't do it.