Isn't a one party system called a dictatorship?
A democracy isn't the most functional or efficient form of government and is not intended to be so. It's a fallacy to think that it is or should be . For the most part, it's working as intended. The power is still retained by the people, conspiracy theories notwithstanding.
Those that want "everyone to work together as one" for "the good of America" are either BS politicians or those who simply don't understand the democratic form of government.