What is culture?

What makes us different? Why are those differences important? Why is it important to maintain cultural heritage/traditions/rituals? Specifically I'm thinking about Judaism, but I think these questions could be applied to anything. Judaism has existed for a long time. Why is it important that it keep existing? (There is the whole argument that Torah is truth, which is a huge huge one, and I don't mean to discredit it, but for the purposes of this line of thought, I'm putting it aside for now.)

Should Judaism be maintained just because it's been around for 3,000+ years? There are other things in this world that have been done for a long time that I don't think should continue. What does it mean for something to have cultural value? How does culture enrich our lives? 4 years ago in France I participated in an intercultural training for young adults from over 10 countries. As others shared their customs and cultural stories, I found little in "American" culture that was meaningful in my life. So my default for speaking about my traditions/heritage/etc. was Judaism. That's where I felt I had something meaningful to add to the conversation, to share in an exchange. Ok, so there's value, so these practices do enrich our lives. But what does that mean for how we treat other people?

It seems we need to belong to something in order to live comfortably in this world. We search for a town, an ethnicity, a club, a religion, a school, a family, a cause, an organization that we can feel an affiliation with. These communities form our identities, we feel lost without them. Yet, continually, over and over, throughout history and everywhere today, these affiliations perpetuate judgment through an us/them mentality. "I'm a democrat and if you don't agree with me, you're wrong." We belong to something to be able to say the other side is less than us.
What is a world without affiliations? Is it a meaningless colorless world? How do we get to a place where we are all looking out for the other? Where we don't shove aside someone in trying to get to a holy site? Where we don't make half-joking-but-still-cruel comments about members of our own community behind their backs or even to their faces? How do we get beyond our insecurities?

I have some ideas, but I'm really curious to hear what you think.