Which tribal league is often credited with providing a model system of government that was later adopted by the united states?

The Iroquois League was formed of five tribes, with a sixth joining later. A council consisting of chiefs and sachems (leaders) were responsible for the league. The Iroquois became a basis for United States Government.

Democracy began in Athens, Greece around the 5th Century BC. Greece was made up of a variety of city-states as opposed to one central body. Cleisthenes is considered the father of Democracy. Prior to Democracy in Athens the city was ruled by wealthy elites. Democracy allowed all male citizens to vote even if they were poor and attempted to spread power out amongst the people.