For marriage purposes, I don't differentiate between Somalis and other ethnic groups anymore. I have realised that the local Muslim culture is the same across ethnicities and only varies slightly between those born and raised here. It is background noise.
I didn't understand at first either, but a lot of Somalis do not acknowledge the fundamental difference in ideology. Once that inevitably sets in, things will start to make more sense.
We are entering a pseudo post-ethnicity future. I'm noticing a lot of marriages between different Muslim communities. I can see that being an American Muslim will be a stronger identity than being a Somali-American, Pakistani-American or any other hyphenated people.
Don't you think you are over-exaggerating the universal Muslim cultural influence a little bit? Yes, Islam crosses borders and occasionally transcends national identity, but you must agree that the modern situation is far from leading to as you put it a "pseudo-post-ethnicity" in the future.
This is because the nationalistic feeling has taken root in many Islamic communities these days, an Egyptian sees him/herself first as an Egyptian rather than a Muslim sadly. The same way a Saudi sees him/herself as different to a Morrocan or a Jordanian regardless of religion.
This is generally also the case in the West even if there is fraternisation between differing Muslim ethnic groups, there is also subtle segregation happening. A Somali area is predominately Somali and an Iranian area is predominately Iranian and as such, there is much less mixing going on as you're proposing.
Yes, there are the occasional outliers that maritally mix but it really isn't as common as you might think. Social media and the internet, in general, give an impression that marriage between different Muslim groups is increasing but an impression is just that, an impression. It doesn't necessarily reflect reality.