There's all kinds of different ways to interpret that movie. 
I've long been interested in all the ways one can interpret TWoO, which is like America's fairy tale (as opposed to most fairy tales we're familiar with, which are European in origin). Here are a couple the many possibilities:
1) I once attended a historical conference where a professor presented a paper about TWoO as an economic parable full of symbols for economic trends and characters that were prominent at the time of its publication. In this scheme, Dorothy represented Everyman, the Scarecrow was the farmer, the Tinman was the factory worker, the yellow-brick road was the gold standard, the Emerald City was the greenback, and the Cowardly Lion was William Jennings Bryan (don't ask me the logic of that last one -- I can't remember the reasoning). I wrote about this once in connection with the big annual Judy Garland celebration in Grand Rapids, MN, Judy's hometown.
2) I once read a book called
Oz. It was about Dorothy, an awkward, unhappy orphan around the turn of the 20th century, sent to live with her aunt and uncle on an incredibly bleak, grim farm on the isolated prairie in Kansas. Aunt Em was distant and emotionally unavailable. Uncle Henry started sexually abusing Dorothy. She had a school teacher named L. Frank Baum, who took pity on her and fantasized about Dorothy escaping her depressing existence by escaping to a marvelous colorful land.
These chapters alternated with chapters about young Judy Garland, her drug struggles, etc., and chapters about a guy in present time who had AIDS.
TWoO also figured into my early writing career. The very first book I ever tried to write was TWoO (I didn't realize you had to come up with a whole new book of your own; I thought you could just write what you knew, a book you were already familiar with). I remember I was so young that I spelled "of," "uv." My dad gently corrected me, and I've never misspelled it since (at least that I know uv).
