Author Michael Horton, Professor of Apologetics and Systematic Theology, has explored that question in his new book "Christless Christianity: The Alternative Gospel of the American Church."
At his website for the book he gives a 5 minute introduction to its message. You can also download the first chapter for a further glimpse.
From the website,
"Christians have always had their differences, but never in church history have there been so many statistics indicating that many Christians today are practicing what can only be described as "Christless Christianity."
Christless Christianity guides the reader to a greater understanding of a big problem within the American religious setting, namely the creeping fog of countless sermons in churches across the country that focus on moralistic concerns and personal transformation rather than the theology of the cross.
Michael Horton's analysis of the contemporary church points believers back to the power of a gospel that should never be assumed."
Check out this especially pertinent warning to the church.
p.s. Do Not miss the link to Horton's article in Modern Reformation linked in the side bar
h/t Phil Johnson