Talent that is evaluated in, effectively, one dimension? Commercializing a product successfully is a highly multi-dimensional endeavor.

Even building a reasonably well-functioning engineering team is highly multi-dimensional.

My 2c is that culture around work (in general - not specific to tech) and pay in Europe are a much bigger contribution than hiring. By no means am I trying to disparage European engineers or those who stay for a myriad of good reasons. But, it's also clear that some of the best EU engineers would rather work in the US for much higher pay. Even companies like Google* pay much worse if you work on YouTube in Paris vs the US.

* at least in the past from talking to peers