Does multiculturalism work? No.
Never has, never will.
Human beings are just not programmed to accept diversity.
Yes . . . . you can make it work on a college campus. Yes, you can make it work inside indoctrination centers once known as the public school system. Yes, you can make it work to some degree in the US military, in sports teams, etc.
As long as you have THE POWER TO PUNISH anyone who disagrees, you can force people to accept each other.
But in their natural environments, most will reject those who are different and seek their own kind.