One of the difficult things to manage about American national identity is that pluralism has to be at the center of it in order for it to work. If we are to be unified at all, it is around the principle of diversity. E Pluribus Unum. A lot of people, it seems, have a hard time getting that.
The problem is, "diversity" has to be understood as a search for meaning. Who am I, if I'm not you? This problem can be understood in terms of sociology (in which I have no expertise; but I read a book once....which is where I get the terms I'm about to use). Put simply, and in the context in which I encountered it, it's the problem of joining the Church of Belonging, or the Church of Meaning and Belonging.
The first you join by accepting the principles of the group, principles which are given to you and by which you are to abide. This is, in fact, the usual view of church many have who either (a) have no experience of church, or (b) had a bad experience of church, or just rejected it after childhood.
The other church, the "Church of Meaning and Belonging," doesn't give you a ready made list of what to believe and how to believe it. Going back to my "tent" analogy, this church provides the basic structure for you, but leaves it to you to decide what you do with it, how much of it you accept, etc. Let me try to give you an example:
I attend an Episcopal church, now, and it's very "high" church, the stereotype, in some ways, of an alienating space to the uninitiated. There is a procession and recession with two crucifixes, a Eucharist served to those kneeling at the rail of the sanctuary (the area around the altar), kneeling benches, people who enter, cross themselves, bow toward the altar before entering or leaving the pews, etc., etc. And yet it is the most welcoming church I have ever attended. No one notices that I don't cross myself reflexively, or bow, or even where I sit. No one even seems to care if I come or not, although they are always glad to see me. The liturgy always runs over an hour, but no one seems to mind.
I have attended churches where you don't sit in certain pews, because you are taking someone's "place," and where, if you don't do things "the way we've always done them," you are in trouble. Of course, the "tradition" there is peculiar to the congregation, not to the denomination. And it is rigidly enforced by the "true powers" of the congregation. Needless to say, such churches are never welcoming, and are usually dwindling, rapidly, into a handful of tired old people who seem to come on Sunday out of habit, and who want to leave promptly at the end of an hour (although where they have to be has always been a mystery to me).
In the latter, meaning is supplied by rigid adherence to "tradition," which is tightly controlled by a handful. In the former, meaning is supplied by you; fit it into the context of the denomination as you can. I have, indeed, met more liberal members in that church, than some of my seminary professors (who were members, some of them, of the Jesus Seminar).
It's a matter, you see, of what unites you. If it is not something from "outside" the community, which provides the structure for you, then you have to invent it yourself. Invention is hard for most people; they shy away from the existential effort. They simply want to belong, and be left alone otherwise. Diversity, for example, means I have to find meaning in your difference from me. And that's hard work. Better to just quash your difference (or ignore it all together) and praise "our" sameness. This is the divide in the country now: between those who want to be in the Church of Belonging, and those who want to be in the Church of Meaning and Belonging. We all want to be Americans: but what kind of Americans?
It's easier to belong, than to search for meaning.