The world is not getting any bigger. It is a global economy, travel is cheap, people move in search of jobs, and now we can make video phone calls internationally almost for free.
My wife and I were amazed a few years ago that you could cross from the Netherlands into Belgium with less evidence of a border than driving from Rhode Island into Connecticut.
It is hard for someone my age to believe that all of Europe uses one currency.
Information, culture (Gangnam Style), money, friendships, language--all flow across borders.
The WORLD is multicultural. The world is getting smaller and mixing of all kinds is happening more and more rapidly. Every place IN the world is going to become more and more like world itself.
I don't want to be smug about the United States, The U.S. is certainly not heaven on earth. It took 120 or so years between the wave of immigration of Irish escaping the potato famine and our first Irish-American (and first Roman Catholic) President. It took 150 years or so between the Civil War and our first African-American President. There is political tension, friction, and--always--discrimination against the most recent groups of immigrants. I think it is quite possible that I will live long enough to see a Latino become president of the United States.
I don't know the details about Italian "multiculturalism." Is that a code for "inclusion of blacks?" Italy is another country and I wouldn't presume to give advice. But just in terms of guessing what will happen, I think Italy will have a black Prime Minister sometime before the end of the century.