Some people say that some Muslim immigrants to America do in fact assimilate. But how can that be the case if they remain Muslim? In the first place, America is not a Muslim country, so if you move here and remain muslim, you have failed to assimilate in that regard. More importantly, Islam is more than a religion in the Western sense — it's also a blueprint for running a society, which includes a governing system, and that governing system is not compatible with our Constitution or our whole concept of how a country should operate.
So, no, a Muslim immigrant, by definition, is not assimilated.
It's hard for a lot of people to understand this, because here in the West, we don't have any religions like that. There's nothing in Methodism or Catholicism that would lead an American immigrant to Pakistan or Nepal or Japan to want to destroy the governments there. Such an immigrant might want to do so for other reasons, but they're not intrinsic in his religion, if you see what I mean. The Pakistani government need not fear second-generation Mormon immigrants being "radicalized" in the local Mormon Church in Lahore and consequently blowing a bunch of people up. Americans can't get it through their heads that Islam is not just a framework for personal morals and salvation, like most brands of Christianity, but a total way of life, that prescribes, really, everything you do, including political things. And don't be fooled by the fact that there are factions within Islam that call for slightly different political systems, and conflict with one another. All forms of it, as far as I can tell, prescribe how a person should live in every respect.
Given all this, how can any Western country, or indeed, any non-Muslim country, even contemplate welcoming Muslim immigrants? It's pure madness. From the Unz Review [link], here's John Derbyshire on the subject: