I agree with Ace, and I think you are wrong.  It's different this time.  There is the evidence of our own eyes based on what is going on in Europe where mass waves of African and Middle East migrants have entered, failed to assimilate, self segregate, and engage in criminal and violent behaviour at rates vastly beyond those of the general population.  There is also a religious / cultural element here that as much as people want to ignore, remains a factor.  Then, there is the issue of numbers.  There were never this many jews, Vietnamese, or Hungarians trying to enter the West all at once, there was time to assimilate, and there was much less contact with the home country once they came here, so they assimilated better and more quickly.  There was less government support for them, so they had to enter the workforce quickly. Now the more children they make, the more support they get.  

Many things have changed, so "past performance is no guarantee of future results".