In our modern world, the culture tells me that my identity is self-made and discovered privately, all by myself. This is not a Christian option. However, given the way that we practice Christianity individualistically, the members that make up the body have no recourse against it.
Let me throw some Christian language on this to show how we have succumbed to this assumption. Today, it is assumed that I am a disciple to the degree that I privately pray and read my Bible as I pursue a personal (read: individualistic) relationship with Jesus. I know God primarily in my private pursuit of him. Therefore, I am the chief arbiter of what it means to be a Christian based on my private prayer and Scripture reading.
When you have an entire Christian culture engaging God in this way and constructing the core of their Christian identities in their private lives, it shouldn't come as a surprise that the answer to the question What is your name? or What is the church? or What is a Christian? will yield a legion of answers. Why? Because all of us are separately being formed by some group of people telling us who we are.
If communities outside the people of God give me cues to the deepest truths about my identity, then I will come to Scripture and to God already formed as a person whose basic identity belongs to some other group. I will then come to the Bible formed as a good member of x political affiliation who watches y news network, or as a good citizen of z country, etc. But Jesus's kingdom will not be set alongside these kingdoms. "My kingdom is not of this world," (John 18:36).
But the Bible tells me who I am! One of the unique features of the Christian faith is that the central figure around whom it is built, Jesus of Nazareth, didn't write any of our texts with his own hand. While we rightly claim to gather around the teachings of Jesus himself, this requires that we trust what John, Luke, Paul, James and others tell us about Jesus. Therefore, even when reading Scripture "by myself," I don't bypass my need for others to bring me to his feet. Without human witnesses, then, I would not be a Christian. Indeed, part of being a Christian calls me to have the discernment and faith to recognize that Matthew telling me about Jesus is coequal with Jesus himself speaking to me. That's why the Bible, although written by the hands of human authors, can be called the word of God.
Christianity is a received faith. Therefore, what it means to be a Christian has already been determined. Our faith has been here long before us, our families, cultures and nations. We don't get to decide what it is, nor what constitutes its practices. Therefore, when considering what are the challenges of being a Christian today, we recognize that our appetites need to be communally formed to think, love, act and read as Christians.
Christian formation happens in communal practices, teachings and worship where we are shaped to read Scripture as members of one body, rather than as modern individual citizens of this or that country, individual members of this or that political party or individual adherers to this or that cultural ideology. Countries, polities and ideologies will always vie for the allegiance of individuals attempting to put lenses on our imaginations by which to engage God, Scripture and truth. But these problems aren't new.