I think having two party system is effective system keeping in mind many reasons. Having different views on different problem helps solving that problem faster. It also keep a party more competing then others which is better in the way. For example war on Afghanistan, Bush was all for the war while obama stopped and controlled countries spending.
If you believe that there is actually a two party system party in the United States you are a fool. There is one force behind two factions,Democrats and Republicans, calling all the shots. It's the capitalist party and it is designed to make the wealthy more wealthy. The media is used to trick people into voting for a certain candidate. One candidate always gets more positive press than the other. When the people calling the shots(the ultra wealthy) need to tighten the budget they put in the big bad republicans to make budget cuts. When the people have had enough and are on the verge of revolt; they put in the democrat to give away the store. Yes. A group of super wealthy people worldwide use the media to push people to one candidate or another depending on need. The game is rigged. There should be no elections for senate or congress. It should be handled like jury duty. You get a notice to serve; however, unlike jury duty, you have the right to decline. Cut congressional terms to one year and senate term to two. The same jury like system could be used on federal, state, county, municipal and basically all elections. That's a government of the people. No media rigging or funding of elections from special interest groups.
Which is exactly why many of the founding fathers loved it. James Madison, the primary framer of the Constitution was a big fan of the two party system. It keeps the politicians at each others throats and that keeps them away from our pocket books and freedoms. The gridlock serves as a guard for our liberties.
As evidenced by the current situation in Washington, the two party system can not be counted on to put the country's needs first. With only two major parties in control of all the organizing and fund raising, it has become an adversarial game where both sides seek only to win. If there were more parties, compromise and being able to build coalitions would be much more valued.