Do they really think of a country born out of genocide just a few hundred years ago is more "adult" than the cradle of civilization itself, continually occupied by humanity since beyond memory, which has seen the rise and fall of countless nations and empires

They do, because to them "history is bunk" and even if it isn't, this time around there are Wunderwaffen and the internet which makes the tides of history irrelevant, so they believe.