Totalitarian government is where the state controls all of society and seeks to control every aspect of public and private life.
Unitary government is where the state is governed by a single power.
Direct democracy is where the people have direct control over what is happening in the government.
In the United States, the state does not control all of society, nor does it seek to control every aspect of public and private life. The US government has three branches: executive, legislative, and judicial, so we are not governed by a single power. People do not have direct control over what is happening in the government in the United States.
The United States national government is best described as a democracy.