1) Isn't America essentially a country where people from all over the world came together to create a new culture? Something called The American Culture? I don't see them calling themselves Soviets.
And what happend? How many speak the same language as their none English speaking ancestors? How strong is bulgarian culture? American culture is MTV and Mcdonalds. Not exactly what I want to see the worlds ethnic diversity replaced with.
Going back to the USA, although there's something called The American Culture, nobody in their right minds would say that all Americans are the same. America is in no way a homogeneous country. They speak many different languages there, and have vastly differing cultures. But do you see them trying to go to war with each other?
One third of all males of a certain ethnic group have been or will be in prison at some point in their life.
Also, no since you killed so much of the diversity.
2) So you're now talking about intellectual diversity. What makes you so sure my ideal situation would destroy intellectual diversity? Let's take one supposedly homogeneous people: the Han Chinese. Can you tell me that they are one blob with no differing ideas? Are there only a few newspapers? For all the censorship, there are still newspapers which criticise the government.
Of course there are differences, I don't believe that there should be one China, I am against the nation state. Native Americans are a perfect example of what happens when you let foreigners in. The Mayans disappeared. Their language is gone, their religion is gone, their culture is gone. Once great civilizations are now run by druggangs.
In America there's Democrat vs Republican. They're all American, and they would never think of splitting America up, but can you tell me that they're all the same? The bloody debacle in Congress is going totally against that.
a republican and a democrat are way more similar than a republican and a person in the kongo. Even so, these small differences lead to conflict.
3) If local freedom gives people the right to hate another group just because they're a different group, I'm not sure it's a freedom I'd support.
People shouldn't hate, multicultralism is hate. It is when ethnic groups get in eachothers way that they kill eachother. Tribes in Africa kill eachother. When did an african tribe last go kill people from Chile? They don't since they aren't in their way.
So what are you suggesting? That we keep all peoples of differing cultures physically apart? You know as well as I do that that isn't tenable at all.
Also, the EU is coming apart not because of the idea but because of the implementation.
Having local independent communities.
Soviet union failed, Rome failed, the big empires failed, the ottoman Empire failed. Eventually either all groups are destroyed or the state falls apart.