I think what we are seeing isn't the death of Christianity, it's the death of cultural Christianity. I don't think we have less Christians in the US, but the unregenerate simply have little reason anymore to call themselves Christian and be involved in a local congregation. The old model of increasing church attendance is to make the church more attractive to unregenerate people. That's not the model of evangelical discipleship that Jesus called for in the Great Commission. In fact, by Jesus' own model, he intentionally thinned the crowds by teaching difficult and unattractive things.The other dynamic to this is the aging church population versus the contemporary Christian movement. Both have their problems as well as faithful elements. Today's old church is still rooted in cultural Christianity which tends to be moralistc but they also practice a steadfastness that younger Christians need to learn. Today's contemporary Christians recognize the problems with the moralism in the old church and enjoy a stylistic freedom that fosters spiritual growth. However, in doing so, they set themselves up for a different kind of moralism. While old hymns have great theological truth, many older Christians don't often practice the truth in those hymns. Contemporary music gets back to the basics, but song lyrics often don't breach into more difficult truth. The contemporary crowd are better at practicing what they ding about, but only because what they sing usually isn't as deep. Both groups have too much pride in their own systems. Steven Furtick illustrated the problem well in a video that Elevation Church has since pulled down called "Haters". Copies of the video can still sometimes be found because the Internet doesn't easily forget. He criticizes the old church and in the process unwittingly acts just like what he's criticizing.So even as many old church buildings go empty, many new ones are being built. I look forward to seeing this documentary.