I think the idea of the melting pot is unrealistic. America will never melt because to do so would require that everyone who comes here give up their cultural background in favour of a uniquely American culture, and I don't see that happening. I think that cultural identity (and by that I mean identifying as part of a larger cultural group, be it Scandinavian, French, Italian, Japanese, Irish, Cherokee, African American, whathaveyou) fulfills a basic human need, and I don't see America (as a single entity) stepping up with anything to fill the hole left when an imigrant gives that up.

The problem comes when part of that cultural identity is tied up in feelings against another cultural identity. That's when you get Irish vs. English, North vs. South, Black vs. White, etc. etc. etc. Ideally America should be a country in which everyone is able to maintain the sense of cultural identity passed down to them through their ancestors, while at the same time realising that cultural feuds belong in the past. I'm not sure such a society is possible, but I'm optimistic.