I strictly believe that one has to produce ALOT of theoretical AND practical knowledge before being recognized as scientist, which is not the US case. In US you write down your 100 pages thesis of nothing, partisipate in a couple of speak-about-everything-and-nothing-in-particular conferences and woah you are a scientist! The value of science is heavily and rapitly devaluating :-(.
PS: Same trend is happening here in Russia.
With regards to your second paragraph (and your prior comment about scientists having to be >30 to be recognized as such and >50 (!) to become one in Russia), the evidence of the works produced by great scientists in the past hundred years strongly suggests that there is something wrong with that belief. Looking only at mathematics, for example, it is difficult to argue that Ramanujan, Godel, Hilbert, Grothendieck, Weil, Weyl, or Deligne (to name only a few), were not truly scientists before age 30 (by which time most of them had published some of their best works).
If the value of science is indeed going down in the US (a fact which is not at all clear to me), then there are lots of other possible reasons for it. But certainly not age.
I am Russian and I can tell you that it is spelled "A LOT". Anyway, you are overgeneralizing about the US education system. It is true that in many universities one can get away with writing 100 pages of nonsense for a PhD, that is not the case in the top tier schools. The entire system is premised on rankings, i.e. top schools produce top scientists who produce top results and get the most grant money. Lower ranking schools produce the "fat tail" of PhDs who are more involved with teaching, collaborating with the industries, going corporate, etc.
In the US, the unspoken assumption is that if one really wants to be a "scientist", they can become one, virtually independent of their ability. I guess the intention is that one's efforts should be harnessed productively vs. generating frustration.