> imagine there are many neighborhoods in large cities where an outsider moving in expecting mass media American culture would not feel welcome

I think they would find neighors very welcoming - even the toughest cities and neighborhoods are mostly friendly people - but the culture would be unfamiliar and the newcomer would have to adjust.

> it may be easier to travel to an area of the city with more generic culture where they do feel welcome

I'm not sure where that is in many cities, other than suburbs. You can't escape the richness of large cities.