The actor for Mat does seem to be a fit. But if the series makes it then that guy will need to adapt and grow. All the characters evolved quite a bit and hopefully someone has thought this through when picking their actors.
Well, if they f it up, we can just burn Amazon to the ground and start again. I can hope since they are going for racial diversity and not by the books that they at least portray the cultural differences well enough that it does not come off as a bland populous through out the series.