It might be considered presumptuous or pointless for a non-believer to talk about the divisions in the Christian religion. But most people in America are Christians of some sort, so these divisions have a real effect on all of society.
When people think of schisms in Christianity, they usually think of differences in denominations. Catholic and Eastern Orthodox, or Catholic and Protestant, are thought of as the basic divisions. But the real differences that divide modern Christians are related to the basic contradiction in traditional Christian theology.
Traditional orthodox Christian theology holds that God is good and loves the human race, and that people who do not believe the right theology will suffer eternal torment in Hell. These two assertions contradict each other.
With the rise of the Enlightenment religious toleration and questioning of traditional beliefs became possible. So now some people tried to deal with the contradiction. What might be called "liberal" Christianity began. The Unitarian Church was the pioneer in this trend. But traditional ideas fight hard against any softening of the fear of hell.
So what we have now is two types of Christianity, and even two types of religion in general, competing for influence in the modern world. One type emphasizes the love and mercy of God, and teaches compassion as the most important value. The other emphasizes the power of God, and teaches fear of God as the most important value. Each deals with the contradiction by choosing which half of the traditional theology to emphasize.
So why is an agnostic like me concerned with this split? I want to have a better society. Which group of religious people are more likely to work cooperatively to make a better society? Those who want compassion for people, or those who want people to submit to their idea of correct theology? The emphasis on compassion can lead to cooperation against the ills of society. The emphasis on power can lead to emphasis on which people have power, and to stronger hierarchy. The emphasis on power and theological correctness can lead to tribalism, with the elect against the infidels. The emphasis on compassion can make it possible to break down tribal barriers and reduce conflict.
As an agnostic, it is unlikely I will ever believe in any theology. I have no problem living with some believers. But those who want rigid theological correctness to frighten people into their beliefs are a danger to my freedom.