The kingdom of Upper Egypt was and remains to this day more distinctively Egyptian than that of Lower Egypt (the Delta). In fact, Lower Egypt never really mattered in Egyptian history until the low period, when Egyptian civilization was in decline.
The attitude of Upper Egyptians towards Lower Egypt can best be illustrated in the Story of Sinuhe ("Son of the sycamore tree), thought by many to be history's first novel. http://www.geocities.com/wally_mo/sinuhe.html
When Sinuhe reflects on two occasions as to why he fled Kemet, he says, "As for this flight made by this servant, it was not planned, it was not in my heart, I did not plot it. I do not know what separated me from my place, it was like a dream. It is as if a Delta-man saw himself in Abu ("The Elephant"; Elephantine/Upper Egypt), a marsh-man in the Land of the Bow(Nubia)." It is in Upper Egypt, from the beginning, that the successive stages of Ancient Egyptian civilization took place.
It is also from Upper Egypt, from Nekhen, that the process of political unification was begun and ultimately achieved by the Pharaoh Narmer. More remarkably, after centuries of foreign domination and invasions, the Egyptian population of Upper Egypt has essentially remained ethnically the same as it was during the days of Pharaonic Egypt, especially among the Upper Egyptian fellaheen. Unlike the Delta, where the influx of Asiatics, from the time that the Delta became inhabitable to the present day, has constantly and consistently changed the ethnic makeup of the Egyptians of this region.