Intermarriage and immigration
asks a couple of questions about the differences in certain racial matters between the UK and US. I think the answer to both is that the US was founded on immigration. There was a pattern of racial "homogamy," i.e. Germans would only marry Germans, Italians would only marry Italians and so on, that has only recently broken down. Britain never had that tradition. A similar argument applies to residential segregation. The Irish went to Boston, the Italians to New York, the Scandinavians to Minnesota and so on. You lived with your people. So a degree of segregation was built in by immigration that continues to this day -- Cambodians flock to Lowell, MA, for instance. Britain has never had immigration on a similar scale, but it sees it to a lesser extent -- Brixton, the East End, Bradford and so on (I have to say I find Paxman's quote very hard to believe).
I also think a lot has to do with the fact that minorities are just that much smaller in the UK than they are in the US. There are only 4 million members of ethnic minorities in the UK, meaning that they find it hard to reach "critical mass" in forming communities. Blacks make up 2% of the population, compared to 13% in America. This also means, in intermarriage's case, the "pool" of possible mates is that much smaller in one's own race, making it more likely that one will look outside that pool for a mate. The US is, of course, still hampered by the legacy of segregation as well, so older minorities are much less likely to have intermarried. But there are signs that this all changed in the younger age groups -- see here
for an examination of the age factor. Younger blacks have an intermarriage rate not dissimilar to that in the UK. The UK got to the position faster, thanks to the factors just mentioned, but I don't see any particular difference between the two positions in the future.
In short, I find this less of a problem than Chris seems to, and also can't see how it is a problem for the Anglosphere above and beyond the historical one of the legacy of slavery.
UPDATE: I now realize I misread Paxman's quote and find it much less hard to believe now I haven't got it the wrong way round...