Sociologists have been noting that Americans are becoming more tribal all the time. We gather in groups that are "like us," and even adorn ourselves with jewelry and other markings that indicate our tribes. We seem to feel a need to distinguish ourselves with our clothing, hair styles, etc.
If you have any doubt tribes exist, ask any 12 year old girl and she will gladly point them out at her school. If you spend a few minutes thinking about it, you'll know you have tribes at your work place, church, or other gathering place, too. This is not the purview solely of teenagers.
This separateness is antithetical to the idea of America as the great melting pot. Bob Edwards interviewed John Mellencamp recently and in the course of conversation, Mellencamp said something that spoke to this idea. He said, "We became more tribal as we tried to take democracy everywhere."
I had never thought about the idea of tribal in this context, but he's absolutely correct. I can't say it's a true statistical correlation, but the idea is sound. As we have tried to spread democracy (for reasons I don't fully understand, but that's another discussion), our own society seems to become more segmented - more tribal.
It's a conundrum.