It's absolutely valid. If you don't understand it, then you don't operate in Christian circles. But I suspect you know exactly what I'm talking about and you are being intentionally dense.
Yes, I am aware of the history of that statement. You'll also note that those countries were dominated by state churches only adds to the confusion.
As for your question, your response to my original answer indicates you know exactly what I'm talking about. If not, then this meme isn't for you anyway.