Earlier quoted context omitted.
Isn't what you are saying a bit extreme? I mean, PhDs in Europe are very short and thus students don't have the opportunity to do that much. So in a way they are quite mediocre. Yet some recover afterwards. But I agree it's hard to revert the trend if you're in a down-spiral.
It's not as straightforward a distinction as you imply, and certainly not grounds for attributing a lower value. In Europe (Germany in particular), you have to do a 2-year Masters degree which tends to be ~1.3 years of coursework and ~0.7 years of research culminating in a thesis. Judged by the quality of your thesis, you then try to get accepted into a group for a PhD which takes 3 years on average. In the US you go…
Imho people make a bigger deal of EU/US phd differences than there actually is. The structure is different, but the end result not so much.