The U.S. national government is a presidential constitutional federal republic and representative democracy with three separate branches: legislative, executive, and judicial. It has a bicameral national legislature composed of the House of Representatives (a lower house based on population) and the Senate (an upper house based on equal representation for each state). Federalism grants substantial autonomy to the 50 states. In addition, 574 Native American tribes have sovereignty rights, and there are 326 Native American reservations. Since the 1850s, the Democratic and Republican parties have dominated American politics, while American values are based on a democratic tradition inspired by the American Enlightenment movement. Since 2010s and early 2020s, the country has experienced increased political polarization and democratic backsliding.

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