As you know, I am 100% Japanese but spent my formative years in the American Midwest. I have a working knowledge of American culture, at least up until the mid-80's, and what's fit for a 14 year-old, anyway. I know all the songs in "Sound of Music" and "My Fair Lady", and I have seen all the Star Wars movies.
And I've seen "Wizard of Oz". I don't know how many times I have seen it, but I know it wasn't once. Or twice. Or three times.
At work today, I was trying to explain the plot of "Wicked" to my co-workers.
"The basic premise is that the Wicked Witch of the West and the Good Witch of the North are college roommates. Are you familiar with Wizard of Oz?"
"Yes, I've read the book."
"Have you seen the movie?"
Well, I guess the average American doesn't know about Chuushingura or Byakkotai, so it all averages out, more or less.