Ah, but you see, in our case you only refer to them as Americans, home-grown, domestic, etc. The moment they change their immigration status and become citizens, the very next day you refuse to accept that they are Muslims, and that even in the second or third generation they "feel more Muslim than American," to borrow your phrase.
You are confusing some things. When people make a deliberate (or in some cases forced) choice to immigrate and take on a different nationality (if allowed after vetting), that might even create a stronger sense of being part of the new homeland, than someone who happened to be born in that country. There are also those who show no gratitude to the kind reception they got to begin with, and there are those who did okay or even fine, in the beginning but got disappointed and radicalized, perhaps due to the bigottery and discrimination they experienced themselves or those whom they feel connected with.
There are all sorts of shades of grey, you as a talented photographer should know that.
But feeling more Turkish than Dutch, not because you or your own parents were born there, but your grandfather was, does raise some questions, doesn't it?
Cheers,
Bart