"Multiculturalism," as it seems to be most accurately defined, is the parallel existence of multiple cultures within a single society.
As far as I know, no multicultural society has ever lasted very long.
The U.S. has never until very recently really been a truly multicultural society, because while there have been regional subcultures (e.g., Cajun, New Mexico, Midwest Germanic), there has always been a clear understanding of and participation in the overall American culture, and the subcultures have tended to become part of the greater culture, rather than remain truly separate.
Part of this is probably because the degree of difference was sufficiently small to allow this to occur.
The problem with today's immigration pattern is that now we have groups that have very, very great differences from the cultures/societies to which they are migrating. Multiculturalism, even if not desired, tends to be the result. It remains to be seen if such differences can be blended into the host cultures.
This is interesting. So you think that the new immigrants from Mexico do not define themselves as Mexicans but as Americans? I would be happy if we could achieve the same in Europe since most problems we have with our immigrants result out of their inabillity to define themselves as Frogs, Krauts or Brits...
Only if the host culture was weak to begin with. In reality one cannot stop cultural mixing and morphing, it's a fact of any dynamic society. If the so-called culture of 'Americanism' is weak it will subjugate itself to new patterns as they come along, and rightly so if it is so weak.
Also, enforced mono-culturalism doesn't last either, because it culls a cultures ability to adapted thus weakening it and usually has to be enforced by the state, which eliminated individual freedom in the long run. In any case identitarianism has a leftist liberal history, and rational conservatives should reject it as childish at best.