I am familiar with the response: "In aeternum. Amen."
In Polonia is it not "Nunc et in saecula"?
Americans do not greet each other this way? In Central Europe the "Catholic Christian greeting" is as natural as are the words in the Lord's prayer. If I'm not mistaken these were also the very first words that right after his election to the papacy the Venerable John Paul II. spoke to the people on St. Peter's square.
Laudetur Jesus Christus.....this is Vatican Radio!