“What rude awakening are Catholics going to have and why?”
They’d realize that their doctrines did not exist from the very beginning, that, actually, their doctrine developed over time, even their claims to the Papacy and the primacy of Rome, and that their religion directly contradicts the teachings of many church fathers.
That’s the summary for you.
Many another Protestant has thought as you do, until he started reading the early Church fathers--Irenaeus, Polycarp, Augustine, Clement, John Chrystosom, Ignatius, etc.--and found to his dismay that from the beginning, Christianity held to the same fundamental truths about the Faith, which Catholicism still teaches.
It's a shock, I know. The Catholic professor of philosophy Dr Peter Kreeft, raised an ardent Calvinist, went through this exasperating process of reading and discovery in the original sources and found himself compelled to admit that the earliest Christians believed and worshipped as Catholics do. Peter Kreeft
So did the brilliant young strict Calvinist pastor and Bible scholar Dr Scott Hahn, whose intense study and agonizing intellectual honesty compelled him to admit the truth of Catholicism. Dr Scott Hahn's Reluctant Conversion
And so did I. I am a simple person and not a great scholar, but though raised as a Protestant, I too had to admit the uncomfortable fact that the earliest writing in Christianity substantiated Catholic doctrine, and that since the sixteenth century, one fracture after another, one doctrinal dispute after another, one prideful man after another who thought he could interpret Scripture better than any of his predecessors in prior centuries, has deviated from the earliest teachings of Christ's apostles.
I invite you to watch those videos. Perhaps intellectual curiosity and honesty will inspire you to read the fundamental works by those men who were instructed by the Apostles themselves. You might be surprised.
“They’d realize that their doctrines did not exist from the very beginning, that, actually, their doctrine developed over time, even their claims to the Papacy and the primacy of Rome, and that their religion directly contradicts the teachings of many church fathers. That’s the summary for you.”
Except your summary is false. As Newman said, and he certainly knew more about Church History than you ever could, “To be deep in history is to cease to be Protestant.”