I originally started writing this in response to another node
. However it rapidly ran off in a new direction
so I moved it here.
I've never been to Chicago so can't comment on the situation there. But I've been to a few other US cities, and compared to London they all seem incredibly segregated. New York City might be a melting pot, but London is the mixing pot: there are more nationalities and more languages spoken here than any other city in the world (approximately 700 different languages).
But despite this, (or perhaps because of this), London isn't split up into the ethnic districts that most US cities seem to be. Most large cities in America seem to have a Chinatown, a Little Italy, a Hispanic area etc, even if they don't have those exact names.
London isn't like that. Although there are regions with a larger proportion of some ethnic groups than others, there is nowhere which is even close to being exclusively one ethnicity. Soho's Chinatown population, for example, is less than 50% ethnic Chinese. The East End inner-city area around Brick Lane have a large Bangladeshi community, but also a lot of black, Irish, Turkish and English people. And Brixton, to some people considered London's Harlem, is actually one of the most multi-cultural, mixed areas in the world: literally every skin colour can be found here.
I'm not sure whether this is a cause or effect, but in London (and in the UK in general), mixed-race relationships are not generally viewed as any different to same-race relationships. Obviously there are some people who think differently (variety is the spice of life) but as a whole, amongst the younger population, it is almost as common to be going out with someone whose skin colour doesn't match yours as does.