They would all ahve been absorbed into other societies. If you look at the present day many of them are losign their culture as it is. Thats not to say all of them, but some are and many are still keeping to the culture and others ahve already been absorbed into the culture of the country they are in.
As for people saying the tribes and tribals are natives, uhh no. During the apoclaypse any small group would probably be considered a tribe. Whether their were natives in it or not.