If anything, South America is overrepresented. Four teams in directly, a fifth through an easy inter-confederation play-off. This is out of a total of ten teams - so, 50% of teams make it in.
Compare this to UEFA, which has 54 teams competing for 13 spots (24%). Going by Skanky's earlier stat, this will leave out six of the top 30 teams in the world.
With all that said, I don't think Europe (or South America) need more slots. The tournament is weighted enough to those sides as it is. If what you're searching for is a truly egalitarian qualification campaign, then the confederations should be ignored entirely, with qualification groups being truly worldwide. That is obviously not what happens, however, and for good reason.
Long story short, keep things as it is, stop complaining.