[ElBorrachoInfamoso]

Stronger cultures tend to overwhelm weaker cultures, even if the weaker culture is brought by a group of conquerors who become the ruling class. Others have already brought up the example of the Germanic tribes that conquered Italy, but eventually adopted Latin culture. Another example is Iberia. The Visigoths conquered Iberia after the Roman Empire fell apart, but they adopted Latin culture. When the Romans conquered Gaul, the Gauls adopted Roman culture. Who do you think had the stronger culture? Today, France is far more Latin than it is Celtic.

Multiculturalism doesn't always fail, it's just prone to failure unless the cultures in contact are relatively equal. Multiculturalism works fine in Switzerland because it is composed of (approximately) equal cultures.

The problem with many immigrant groups in the US is not multiculturalism, it's crime, poverty and the welfare state. Except for a few communities, Hispanics in the US are far more American than they are Hispanic. As a Latino and someone who has spent significant time in Latin America, I can tell you that American Hispanics are just that, Americans first and Hispanics second. They may take pride in their "otherness" and call themselves Hispanic, but their culture is far more similar to American culture than to Hispanic culture. On the whole, Latin America is adopting North American culture more than North Americans are adopting Latin culture. Anglo culture is stronger than Latin culture.