The US has a two party system. We don't abide those third and fourth parties because that's just too many and a recipe for chaos. In fact, I reckon two parties is one too many. Let's cull it down to one and call it The Party. Things would be a lot simpler that way. Party members would decide things for the country, and only the best and the brightest would qualify for party membership, as long as by best and brightest you mean adherence to the party line.
As long as we're simplifying things, let's admit it: there are just too many countries with divergent forms of government and interests that inevitably lead to conflict. Once we get the The Party in power, we can start annexing some of these other countries or, at the very least, make sure that The Party runs them even if they continue to exist nominally as "independent" entities. Eventually, The Party will run the whole world.