Questions about figures like Medes and anachronisms in the Torah

Hello Rabbi Michael, regarding biblical figures such as Media, Egypt, Greece, Canaan, Cush, etc. How is it possible that these people were considered the fathers of their nations, since the chance that all or most of the members of a particular nation would be associated with a single ancestor is slim (in the case of Israel, it can be argued that there was a deliberate hand in the matter, since the giving of the Torah shaped Israel into a nation, but I don't think there was anything similar to other nations that caused them to be formed). In other words, can't it be argued regarding these figures that they were "invented" in retrospect? For example, I could write a story today that claims that there is an ancestor named Americo (the father of the Americans) and another person named Brazil (the father of the Brazilians).