Members of our 2 party system make laws and and regulations related to elections. They have in the past and will likely continue to cooperate to insure that a 3rd party will not have a reasonable chance to become viable.
Most Americans however or either ignorant of or complacent about this. So, for the time being, we are stuck with what we have. OTOH perhaps the phenomena of social networking can have some meaningful effect on this, at some point.