Historiann has a very insightful post on the way that evangelicals have tried to claim the term "Christian" exclusively for themselves. She writes:
Over the past few decades, evangelical Protestants have commandeered the blanket term “Christian” to refer only to their brand of Christianity. Instead of calling themselves “evangelical Protestants,” or aligning themselves with a particular doctrine or faith tradition, they call themselves “Christians.” This strikes me as a particularly obnoxious form of “Christian” imperialism–seizing the term exclusively from themselves, and implicitly denying it to other Christians. Evangelical leaders downplay the role of tradition and doctrine in their own beliefs and practice, so they don’t teach their flock that Catholics, Episcopalians, Eastern Orthodox, and Presbyterians, for example, are Christian too. Since most evangelicals have little sense of the complexities of the millenia of Christian history between Jesus and Jerry Falwell, many young evangelicals are ignorant of major religious and historical turning points like the Reformation. Accordingly, many young “Christians” of the evangelical persuasion are unaware that Roman Catholicism is one branch–some would say the main trunk!–of Christianity.
Historiann is on the mark here. As a faculty member at an evangelical-oriented college (actually, I think it is the same college her "friend" used to teach at in the 80s and 90s. I think this so-called "friend" is also a friend of mine), I have been trying to teach my students this very lesson. I have spoken to Catholic students who have not felt comfortable in this evangelical environment because many of their fellow students come from homes and churches steeped in evangelical anti-Catholicism. (I was raised Catholic and became an evangelical in high school. For the longest time I believed that when I left the Catholic Church I became a "Christian."). I recently had a chat with a Catholic student who was shocked when a fellow student thought all Catholics believed that Mary was God and should be worshipped.
The comments section of Historiann's post has a nice conversation about the meaning of the term evangelicalism. Let me throw in my two cents, borrowed largely from evangelical historians such as David Bebbington and George Marsden. I would define an evangelical as a Christian who believes in the "New Birth" or the "born-again" conversion experience, upholds the divine inspiration of the Bible as a spiritual and moral guide for living, and takes seriously the "Great Commission" mandate (Matthew 28) to spread the gospel throughout the world.
Evangelicals can thus be found in all kinds of Protestant denominations, not just mega-churches or storefront congregations. I also know a few self-professed evangelical Catholics. Many evangelicals believe that they are direct descendants of the Protestant Reformation. Evangelicalism was present, to an extent, in Puritan New England, but it really hit American shores with force in the eighteenth-century revivals known as the First Great Awakening. It came to define American culture in the early nineteenth-century revivals known as the Second Great Awakening.
The bottom line is this: All evangelicals are Christians, but not all Christians are evangelicals. It is time that we get this straight.