I don't know where you live, but here Arabic and Turkish Music (especially "rap" performed by these groups), attitudes and even language (I regularly hear turkish/arabic slang) clearly have a large influence outside of their respective migrant cultures.
>I went to school with children of Italian, Portuguese, Turkish and Greek backgrounds (mostly the parent generation migrated) and none of them were distinguishable in terms of "broad" culture from those whose grandparents were born in Germany.
I had a simmilar experience in my school. But we also had a lower tier school right next to us where that clearly was not the case. And there Turkish/Arabic influence was very clearly greater than any German one.