“The borders have changed little”—- All you hav to is look at the map of the world from 1900 to 1960.
“Arab nationalism puts Arabs before religion.” —— To your point, Egyptians were not Arab, nor did they speak Arabic. Syrians (Assyrians) were not Arabs, nor did they speak Arabic. Moroccans, Libyans, and Tunisia (Berbers) were not Arabs, nor did they speak Arabic. Iraqis (Kurds, Assyrians, Armenians, Azides, etc) were not Arabs nor did they speak Arabic, Libya was not Arab, nor did they speak Arabic. The Sudan (tribal Africa) was not Arab, nor did they speak Arabic, Tunisia was not Arab, nor did they speak Arabic. Why are they all called “Arab” Countries, “Arab” States, belong to the League of “Arab” Nations, and have to live under some form of Islamic Sharia?