It may be dying in Europe and North America, plus the more metropolitan areas of Asia. If you travel to Africa, South America, and in the less developed portions of Asia, you would find that Christianity is very much alive and doing quite well. There are more Baptists in the PRC today than there are in the US for example. Baptist house churches there are usually called “the healing places” and not churches.
Christianity has always been a counter-cultural theology, more at home with the downtrodden and poor than with those that have a prosperous life to manage, filled with luxuries to accumulate and hoard. A plain reading of scripture indicates that an attempt to fit materialism, gluttony, self-sufficiency, and the childish desire “to be happy” within authentic Christianity is a tall order. The American experiment in trying to do that may be coming to an end.
One could argue that the Christian church in the US essentially yielded its duty to feed the poor, care for the sick, and parent the orphaned to the government. In the process, it took the easy path of letting the bureaucrat replace the local congregations, pastors, and deacons in providing the social safety net. We Americans are fond of the easy path.
Simply put, if the church is no longer showing the love of Christ in tangible ways, it becomes little more than a social club (at best) or a clanging gong of loveless bible thumpers and a political movement (at worst). In Africa, the church is often the only thing between some inhabitants of a village and starvation, but the people of that village are actively engaged and living out the vibrant and active New Testament theology.
“‘I know your works: you are neither cold nor hot. Would that you were either cold or hot! So, because you are lukewarm, and neither hot nor cold, I will spit you out of my mouth. For you say, I am rich, I have prospered, and I need nothing, not realizing that you are wretched, pitiable, poor, blind, and naked. I counsel you to buy from me gold refined by fire, so that you may be rich, and white garments so that you may clothe yourself and the shame of your nakedness may not be seen, and salve to anoint your eyes, so that you may see. Those whom I love, I reprove and discipline, so be zealous and repent. Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me. The one who conquers, I will grant him to sit with me on my throne, as I also conquered and sat down with my Father on his throne. He who has an ear, let him hear what the Spirit says to the churches.’”