You’re right about the characters in the books being European. However, their race isn’t central to their characters. Rand is really the only one that it actually slightly matters for because of the Aiel, but the actor playing Rand is a red haired white dude, so he matches the book at least in that respect (don’t know if he’s tall enough). If the Aiel show up and are all a different race, then it would be a problem. But it doesn’t really matter that Perrin and Nyneave are black, or that Egwene is Australian.
I get wanting characters to look like they are described originally, but most of the time, that’s the LEAST important aspect of a show.
Like I said in the other thread, the showrunner, Rafe Judkins, is a HUGE WoT fan who really wants to do the series justice. I’m not so worried about it yet.