What is a “credential society"?Is there too much of an emphasis on credentials in the U.S.? If so, how might this be harmful? To whom? Have you...

I do not know whether there is more of an emphasis on credentials in the US than anywhere else, but I do think that we do emphasize credentials too much.

I've been, in my opinion, on both sides of this.  Before I started teaching high school, I had been teaching in college.  But because we require credentials, I had to spend a year getting a teaching certificate that did very little to make me a better teacher.  On the other hand, I got paid better than other first year teachers because I had a Ph.D., which did not necessarily make me a better teacher.

As far as the reason, I think it is functionalist.  It gives decision-makers an easy way to identify who is (allegedly) competent.  This lowers the costs of hiring people, which should help society as a whole.