While I understand this, remember that there are entrpreneurs, and then there is the subset of 'tech'. You won't find Richard Branson to fit the 'tech-startup' mold, but he's certainly an entrepreneur. And a pretty good one at that. Many, many people in europe privately fund all sorts of high-end businesses. They just don't use VC money and nor do they always go public. So the data have some variation of "survivorship bias", but in the sense that these data (ie, true survivors) are invisible if you are using a tech/ipo screen.
The only reason I mention this, is that its all-together quite likely that there are some very talented people out there, in europe, who will undoubtedly have what it takes to do what needs to be done.
The better explanation as to why silicon valley does not exist in europe, however, is just cultural. The US has NASA, Los Alamos, White Sands, Area-51, and all kinds of massive experience with science/industry and the types of invention and "productisation" of technology that comes from having huge deserts to play with expensive toys (rockets, weapons). That does not exist in europe, neither the culture, the money, nor the geography. And as a point of history, that to me is a better explanation of why silicon valley is where it is in terms of leading the commoditization of technology, and being the lynchpin a broader market.[#]
Tech entre-preneurialism is a sub-set of this market (ie, many SV firms are huge, or government centric). And thats why for tech-startups, you will always over-represent in SV, because of the larger ecosystem to which VC is a subset (of funding, to wall-street and the government...which underwirite BigCo tech still).
The other thing that is relevant is culture. But in a different way than it is often portrayed here. The ambition of many middle-class people is to strike it rich... "to live like a european". Obviously, this won't motivate europeans...for two reasons. The less obvious reason is lack of social mobility; the more obvious reason is the obvious one (ie, they are more worried about keeping a good thing going, than rebuilding a good thing from scratch).
This might not be a perfect explanation, but even as a straw man its worth considering that there is some truth in it.
[#] While the wealth and brains exist in europe, the critical-density of (capital, expertise, experimental sandbox) does not.