This movie is all about creating your own reality, not in the sense of separate spheres of being or anything strange like that, but in the sense of creating your own space. It's the idea of knowing what is good and promoting that instead of focusing on or being distracted by other things. The Oz of the film is very much an outer representation of Dorothy's reality: her friends from the farm are there (as a lion, tin man, and scarecrow), her enemy is there (in the form of a witch), and her need to stand up and realize what is important to her and what she has to do to keep it is there. Her journey is realizing what in her life is good, and her action is deciding that she will uphold what is good. She can love her home because she realizes that she cares about all of the people who are in it--and that is what makes a home lovable.
The Wizard of Oz, despite taking place after the pioneers, is thematically very linked to the American pioneer spirit--which still persists today, though in different forms. People who moved into the prairie and into the West were moving into new spaces and making them their own. They came with an idea of what their lives could be and of what these spaces could be--and though they weren't all successful in all of their ideas, they did succeed in shaping ground into homes and setting up cities that remain in place many years later.
I guess I've been thinking of this concept lately: that there are so many negative things (small things or big things) that are so easy to talk about and complain about and pick on, but that what we really need to be talking about and focusing on are the good things. Now, I'm not saying that we ignore problems; I'm just saying that in order to make things better (and this can be anything from clothing to world peace and anything in between), we need to talk also about what is good and what can help.
We need to create our own spaces: we need to remember how fluid things are. We need to remember how much of an influence our every word and every action has. Do we want to have a negative influence or a positive one? Do you love your home, Dorothy, and do you want to love and cherish it, or do you want to just try and run away and let it be abandoned?