Final answer:
The American government discourages small parties via the Electoral College system, burdensome local election laws requiring numerous signatures for third-party candidates to get on the ballot, and a plurality voting system that favors the two major parties, making it very difficult for third parties to gain significant support or electoral success.
Step-by-step explanation:
The American government discourages small parties in several ways. One major factor is the Electoral College system, which leads to a 'winner-take-all' situation in most states, making it difficult for third parties to gain any electoral votes. Political scientist Gary W. Cox has noted that the relative prosperity of the United States and the relative unity of its citizens have prevented the formation of large dissenting groups that might support third parties, as well as the lack of regionally dominant ethnic minorities that might form their own political parties.
Local election laws also pose significant challenges for third parties. For example, individuals who are not affiliated with a major party often face the burdensome requirement of collecting thousands of signatures to appear on ballots. Additionally, political parties play a critical role in the formation of policies and legislation, entrenching the two-party system. Parties like the Democrats and Republicans benefit from a range of informal systems and customs that support their domination, such as primary practices and organized party structures like committees.
Finally, while other democracies use proportional representation to allow multiple parties to share power based on vote percentages, the U.S. sticks to a plurality voting system, which further advantages the two largest parties. Although third parties like the Green Party, Constitution Party, and Libertarian Party do exist, historical electoral rules have functioned to maintain a stronghold of the two-party system, making it extremely challenging for third parties to succeed nationally.