Saudi Arabia is the perfect example. 33 million and of those 33, 9 million are foreigners who live there and work but they don't have any citizenship. Somalia could be a little diverse like Saudi but foreigners are not allowed any citizenship but instead have to have a residence permit and they would not be the majority.Imagine how boring one ethnicity nation would be.
Same people, same food, same music,similar lifestyle, same tradition, no new experinces. Shit would be dead wallahi.
As much as i love my people i wouldnt want to live like that tbh.