Anyone who actually reads the New Testament closely will see that modern American evangelicalism is not especially closely related to what those texts actually

Anyone who actually reads the New Testament closely will see that modern American evangelicalism is not especially closely related to what those texts actually say. (Obvious example: the texts don't claim "inerrancy" anywhere.) It follows that Christianity evolved into its current form from the NT as its starting point. Further evolutions and shifts should be expected (though some of them may look like explorations of very ancient paths not taken, like a drift away from inerrantist literalism and back towards things like Origen's opinion that the NT writers may well have made factual errors).