Who says they're claiming to be Christians at all? A staggering number of Americans hold no deeply held religious belief at all. That was my point in the first place. Religion is easy to ignore in our largely secular society, so religious discipline isn't likely to yeild profound results.
I directed my concerned to the Church itself, to those within who ARE serious about living out the precepts taught in Scripture. This number is not as insignificant as you think. The fact that divorce is accepted and counseled in many supposedly biblical churches in the same numbers as the unbelieving world is appalling.
I think you're wrong about the number, percentage-wise, of Americans who hold no deeply held religious belief. Many are just deceived and lulled into complacency by a Laodicean Church. If the Church truly lead the way in proclaiming the truth, instead of bolstering and enabling a secular belief system, I believe you would be surprised to see how many would respond in obedience. But the Church is dreadfully sick, it's leaders lead double-minded, sinful lives and teach those under them to do the same.
A true stand for biblical morality and reform in the Church would no doubt result in a culling out of many, maybe most, of the herd, but the result would be refreshingly healthy spiritually and would ultimately attract those with a true hunger for the new life. "Quality, not quantity" should be the nature of the call.