America’s two party system is interesting and I never thought about it until I moved away and started voting in elections in other countries. While I lived in New Zealand, they had two main parties, National and Labour. but then they overhauled their electoral system without much fuss. It was really quite something to watch. The new system actually encouraged new parties to emerge and soon there was quite a number of them. There were Maori seats that had always been there to represent the indigenous population, Green Party, New Labour, Christian Democrats and so on… Governments then have to form coalitions between themselves and other parties and agree on how to vote and debate on certain issues where those two parties are different.
I remember watching in horror as a small party suddenly held the balance of power in the government in 1996. You can see what happens by following the Wiki articles here: http://en.wikipedia.org/wiki/New_Zealand_general_election,_1996 It was pretty dramatic, but the elections happen every 3 years and the party power isn’t as entrenched as it is in the US.
I think it suits the corporations to only have to deal with two parties in the US so that they can continue to run the country.