Why are partisanship and a two-party system significant parts of US politics?

It brings a divided mentality through politics and through everyday life. Every one thinks their oppionions or beleifs have to be black and white and right in line with their party. One the other hand it provides canadates a larger amount of votes in their population by bringing a larger suport through the party. The second half is why the system stuck in America even when significant fathers advised aginst forming parties.