I don't know, it's so completely complicated. I would think we'd have to move to a parliamentary system to really break the duopoly. The media demonizes and marginalizes any other political parties in America, and Americans want to be "winners" so some even vote for a party based only on the perception that they will be the triumphant side.

The problem is that it seems like for most people, choosing between a few options is preferable than to have to carefully examine and choose from a wider array.