It all boils down to one basic problem : the President has got too much power. A country shouldn’t elect just one person who then chooses their cabinet. To represent fairly all the kinds of ideologies that exist among the population, more than one person should be elected in the executive branch, so that more than one party can be represented. I speak as a Swiss citizen. In Switzerland, 7 federal councilors are elected for the highest executive branch ; that allows for at least 4 different parties to be represented. On lower levels, you usually have 6 or 7 different parties seating in parliaments, which means that none has a majority, and they have to work together to pass legislation. When more parties can access power, more parties can actually exist.