DAFUQ ? I am a French research in computer science, now working for a company producing and streaming contents on the web.
I can assure you that my carrer opportunities — as sysadmin, researcher, or developper — are pretty good in France and in Europe :)
Re: sysadmin and developer roles - my post was mostly about diversity and breadth of available roles. These sysadmin and developer roles are generic enough that one will be fine in them in Europe. A sufficiently specialized researcher, on the other hand, usually has only a handful of places in the entire world that are interested in hiring him within his specialty - a lot of which are in the US.
I see this in a friend of mine. He's a young PhD Machine Learning Researcher with top credentials (Ivy League, top publications, won awards in his field). He wants to live in Europe due to family concerns, but he really can't find a position that would allow him use his talent, and is semi-wasting his time in random bad Data Science jobs for now - while he's getting numerous awesome offers from the US (like leading a research unit at Google or faculty positions in Ivy League schools).
My experience has been the opposite in terms of difficulty. In most EU countries the market of software engineers who can also speak the native country's language is really small so its way easier to stand out from the crowd. In the US, you have to compete in a 350 million+ population pool plus global candidates who have studied English their whole lives. In any given EU country the candidate pool is a fraction the size and of those the one's who can communicate fluently in the native language is a fraction of that fraction.
For example, in the UK, there's little real tech companies and most developer roles are confined to non-tech support roles in other economy sectors (finance, retail etc.).
San Francisco: 170
New York: 96
London: 90
Boston: 38
Berlin: 34
That is debatable and depends largely on a definition. My viewpoint is that a large portion of the companies in the current VC-inspired "tech" world are merely applying tech and not really developing it. For every company like Datastax there's a dozen of companies which are just applying tech solutions (packaged and sold by other companies) to a specific business/consumer problem.
Or, to put it in other terms, if the job offer does not say "Msc/PhD in X preferred" (where X is the job, like distributed systems, deep learning etc.), then it's likely not quite a "real tech" job.
That might or might not be a bad thing. It means you're more likely to be working for a real company, with a real business model, rather than some freak kept above by advertising and VC misallocation.
There are top-shelf jobs for your friend in Europe. E.g. Google's got large offices in London and Zurich and a quick search shows some possible fits for a PhD in ML. I know from friends that Amazon has a large office in Berlin focused on machine learning research and applications. Microsoft appears to be hiring ML scientists in München.