The key differences between the U.S system of government and a multiparty system of government is that the U.S system allows only two parties (Democratic and Republican parties) to contest elections while on the other hand, the multiparty system allows more than two parties to contest elections. Another key difference is also where the multiparty system legislative seats are allocated to parties in proportion to the percentage of votes they win in elections in contrast to two-party system that conducts separate elections for legislative seats.