It seems almost as if different languages are perceived differently
They are. I did some sociolinguistics at uni, fascinating how different languages are perceived, and how valued they are.
Someone speaking 2-3 European languages is thought of as clever, someone speaking 3 Indian languages, not clever.
The politics surrounding language and language use is interesting too, whether something is regarded as a language or a dialect.
It's certainly an interesting question as to why people from certain communities are so well integrated in some areas, and so poorly integrated in others. It does beg the question as to what makes the difference.
I think a lot (IMHO) is to do with there being multiple groups. I know that at least one of the northern towns that now has 'white' and 'asian' areas it used to be RC and protestant areas.
Places I've lived where there has been diversity such as London and Leicester there is multiple diversity. When there are just 2 'groups' or cultures then the differences can stick out. You are born into one group or the other, and your group is 'normal' and the other is 'wrong'. It can apply to anything, language used, the way you go to the toilet, the food you eat.
But where your 'group' or 'culture' is part of many then the things you do, the food you eat etc is just one of many ways to do things.