I think the UK is entirely different. It has gone a long way down the multi-cultural road, quite successfully, but is now questionning how much further they should continue, and at what speed. That is a legitimate discussion in my view
In as much as we don't behave, among 'the cultures' like they do/did in 'Yugoslavia', yes, a ripping success. However. . . .
Multiculturalism is a very strange concept. The 'ism' gives it the gravity of a doctrine, like 'communism' or 'pacificism' or 'nazi-ism'. So what is it about 'multiculture' that is so portentious it constitutes an 'ism'? The only possible answer that it has become a 'doctrine', i.e., something to strive for.
Why on earth should anyone want to strive for multiculture?
To answer that one needs to ask 'what is multiculture'? When I was a naive pale lefty, I assumed it meant that you could cook a curry and wear a sari (or indeed, your girlfriends undies) in the comfort of your own home without fearing that you'd be deported or, at very least, have a brick chucked through your window. Live and let live. I personally hankered to be left in peace despite my strange tase in clobber and music, and I expected someone with black skin to be likewise left in peace. And date or marry someone from a (very slightly, after all) different gene pool. I never thought it meant that the various bonkers doctrines and prejudices that I (were I an immigrant) had left behind when I emigrated to Blighty would be tolerated, and even encouraged. I never thought it meant using British taxpayers' money to fund faith schools (other than C of E ... its traditional, albeit not for me as I am an athiest). I very certainly did not think it meant I shouldn't say 'Christmas' at work in December in case it offended someone (anyone who has mates in the US will know what I'm getting at here; happy Hannaukah, by the way).
So, multiculturalism as a doctrine that promotes the proliferation by taxpayer funding of non-indiginous culture seems to me a bit . . . weird. Why? What for? I like to find out about different cultures, and I deplore racism, but I can't fathom a doctrine of subsidising the proliferation of new stuff just for the merry hell of it.
In the US, for all its faults, the culture dictates that you are American first. I would be very happy if our culture took the same line. Mind you . . . English or British? That is the Elephant in the room as far as I am concerned . . . best address this one first as it is the biggest threat to the unity of the UK (UK? Am I British, English or UKish?). Time for bed. Nighty night.