Unfortunately the problems associated with both phenomena are not restricted to the past. Today, as in days gone by, Christianity and the church are both influencers (so to speak) and influenced by the world around them. While it is good when biblical Christianity influences the surrounding culture and when Christianity addresses the culture in a relevant way, it is not good when the culture leads to a selective and idiosyncratic reading of Scripture and a redefinition of the faith. The problem is often compounded by the subtly of the exchange. In other words, it often happens without people realizing it and as a result Christianity gets mixed up with all sorts of things that have little or nothing to do with the gospel to the detriment of the gospel.
One antidote is to read and re-read the Scriptures, all of the Scriptures, until we are thoroughly saturated with their content. Scripture will correct our understanding of Scripture if we are constantly exposed to large portions of it and not just our favorite passages, or the sermons and books of our favorite Christian interpreters, preachers and apologists. Today in some circles too many listen to talk radio hosts more than they read the Bible and it shows in the way they view the world and consistently misread the dominant themes of Scripture.
Another way to avoid or minimize the negative influence of culture on our understanding of the faith is to study history. When we get some idea of the past and how we arrived at where we are today then we are in a better position to assess current trends and ideas. Human beings are human beings and though we live in different times and places we tend to make the same mistakes over and over again. A growing knowledge of both Scripture and history will go a long way to make us wise interpreters of the "mess we are in" and it will help us know how we should proceed in the future.