Given that this is without a doubt the most non-Catholic Christian nation in history. The fruits of the predominate faith defining itself primarily by saying it is not Catholic are pretty clear. The doctrines of the non-Catholic religions that say each individual can interpret Scripture and live their life according to their own interpretation of Scriptue have totally permeated American society. The consequence is that when the majority of the population is comfortable with interpreting the Word of God to suit their own preferences and preconceptions, they feel free to interpret everything else for themselves as well. The result is just what we see in this country today, a relativist, humanist, selfish, society where no one accepts any authority as being higher than their own authority.
No matter how anyone tries to hide from it, Protestant and Protestant derived Christianity lead to an ever less Christian nation as individuals become more confident that they are in every way their own god and their own master with no reason at all to inconvenience themselves a bit. The majority of folks in non-Catholic churches will tell you that how they live makes no difference as far as whether or not they're going to be spared the flames of hell. So, the predominate religion is really, eat, drink, and be merry, for tomorrow you have a mansion in the burbs of heaven anyway.