It turns out there is plenty of assimilation going on. Cubans and Vietnamese, for instance, are economically indistinguishable from natives. Germans are indistinguishable both culturally and economically. Some cities are doing better than others at assimilating newcomers. Houston, where Mexican and Central Americans predominate, has an assimilation index of just 19. New York, where no one group predominates, has a score of 31.
There's some bad news, too, but this much is good.
"The presentation or 'gift' of the Holy Ghost simply confers upon a man the right to receive at any time, when he is worthy of it and desires it, the power and light of truth of the Holy Ghost, although he may often be left to his own spirit and judgment." --Joseph F. Smith (manual, p. 69)
Be pretty if you are,
Be witty if you can,
But be cheerful if it kills you.