One quick benefit of two party system

The USA will never really have a federal party outside of the Democrats and Republicans. It's just too hard for someone to emerge. But there are pros to the problem. Take for example, Canada and their political system. On any given federal election there could be 6 parties in the running. The right-wing Conservatives, the central Liberals, the left-wing NDP, the Green Party, and any independent (if in Quebec then the Bloq). Usually it's only 4. Regardless, the Greens don't fair well, but between the two left leaning parties (NDP & Liberals) They split the left vote. The left would always win in Canada if it wasn't for this split. Although in america the party lines are really iterations of centralist parties, at least you can make a clear decision (or least the options are severely limiting thus forcing you to chose).