I’ve only spent a few weeks in Muslim countries, and many years ago, but I would say there were two things that were exceptionally obvious differences from the West even to a casual eye:
a) Religion is an incomparably more central part of everyday life than even in relatively religious communities in the West. In the US, being on the extreme end of religiosity means you go to church multiple times a week, and have a social network centered around your church and church activities. In Muslim countries, the muezzin’s call to prayer is broadcast at you five times a day whether you are particularly religious or not, Ramadan changes the daily schedule of pretty much everybody, and so on.
b) Young men- even into their late twenties and thirties- spend a lot of time in large groups of young men, segregated from women. A family friend, who has spend a fair amount of time in Horn of Africa countries, calls this the “homosociality of Muslim life.”
You often see somewhat handwringing essays after yet another terrorist attack by Westernized Muslims that point out that the perpetrator wasn’t particularly religious, and that use that fact to deflect blame from Islam. I don’t have strong opinions about whether Islam as a theology encourages or discourages violence– obviously it does both at different times. But it does seem clear to me that, whether for reasons of deep culture, familial environment, or other causes, Muslim men are more likely to require the structure of an enveloping religious environment and the support of masculine friendship. Western non-Muslims have their own troubles dealing with the withdrawal of these two organizing principles from modern life– basically modern literature is a record of the alienation created by their absence. But we are evidently more adapted, by genetics or socialization, to do without them.
I had several- maybe a dozen all told- Muslim students when I was teaching. They were mostly good students, and they were all good kids, and the pressure of being a Muslim in New York in the years after 9/11 produced no more evident bad effect than the effect of any other social pressure on any other American kid. Recognizing that our power to assimilate Muslims into our existing society is limited- and will become more limited as larger numbers arrive, as the experience of several European countries has shown- does not entail excluding those Muslims who are already here from the circle of American life. Realism about the challenges implicit in our multi-ethnic society does not require us to abjure the people who already make it up, just to admit that further changes will make things even harder, and that we are allowed to slow down or stop now.