The biggest example of culture shock I've encountered so far was an unexpected one. While Christmas decorations were certainly ubiquitous in Argentina and Chile, they were, for the most part, relatively tasteful. Stores would have a wreath on the door, streetlights had standard snowflakes or twinkling lights. Houses might have had candles and wreaths, but not a lot more than that.
It's difficult to describe the experience of seeing the first behemoth inflatable snowman riding a motorcycle, 10 foot snowglobe, or 2-storey Santa Claus. It gets even harder to describe when you've been completely out of the country, thousands of miles both physically and culturally from the Griswolds. Fortunately, seeing houses along these lines has really put us in the Christmas spirit, significantly accelerating our acclimitization process.
It's as if someone greeted us at the airport. "Welcome back. The little lights are not twinkling."
On a completely unrelated note, as I've typed this entry, the "save now" button underneath the window in which I'm typing has grown with each keystroke. It's now several inches long, and it looks weird.