I have some explanation for why Americans and Europeans have this point of view. For one thing they have a history of living in countries where historically an ethnic identity is more or less the same as a national identity. The Germans get a country because they are German, and the French get one because they are French. The Scottish want their own because they are not English, and likewise the Québécois want their own country because they speak a different language.

But it's never been like that in the Middle East, where there are hundreds upon hundreds of ethnicities and languages, who have historically belonged to nation-states that were not defined by ethnicity. Where it's entirely unsurprising to find the next village over the hill speaking their own almost-extinct ancient language that nobody else does. Does that village need an independent country too then?

The other aspect is that in the West many find it convenient to sum all the troubles in the Middle East up by saying the place is full of people who hate each other over matters of religion and race, who would go back to killing one another the moment some strongman is not terrorizing them. That conveniently hides the role of oil in supporting dictatorships (who need not be economically productive to hold on to power because of it), and it erases any guilt the the Americans and Europeans might bear from having had a hand in causing it, whether by meddling or supporting coups or outright invasions. Different ethnicities in Syria and Iraq have been living next to each other for some six thousand years. These are not stranger, they don't turn on one another unless there is some deeper cause for desperation.

Anyway this Western notion of dividing up other countries along ethnic lines is extremely stupid and whenever tried has led to disaster. The people suggesting it are approaching it as if they're giving relationship advice to some couple, who have to break-up because they don't get along. That's the level of thought going into these suggestions.