I use 1500 as a somewhat random reference. I don't think we'll give up the scientific method or many of the advances in medical treatment. (baths are good for you, we know that and won't forget it.) But the world will look like 1500. No long distance travel except for a few brave souls. Distant goods will become extremely expensive. Gold/Silver will regain its status as the official currency.
In the more enlightened places there might be a few libraries and universities. But in the deep rural South and in many other countries, a religious theocracy could rule. We won't live through the transformation but at some time in the next few centuries, large portions of today's rational thought will be lost. Powerful religious leaders will win the battle of thought in places without First Amendment's to stop them. Evolution isn't in the Bible and thus doesn't exist. Women are property in the Bible, God forbid we ignore this important "fact."
It doesn't take much to turn Backwater, Alabama into Medieval London.
I dunno, I bounce back and forth on what will happen. We don't know enough about the Sheple to understand how they will react. In the coming years, we will learn. But at that point it's kinda too late.