The Sumerians are recognized by historians as one of the first groups of people to meet all five characteristics of an advanced and complex society. By 3,000 BC, the Sumerians had already built several cities that were surrounded by fields for farming. While these cities shared a common culture, they operated individually in terms of their government. These independent cities are referred to as city-states which are run very similarly to how a country is run today. The Sumerian city-states include Uruk, Kish, Lagash, Umma, and Ur.

answer; i believe its called ; checks   and balances;

the federal government of the united states was established by the constitution. us is a presidential republic. the president is head of state, head of government and of a two party legislative and electoral system. the supreme court balances the powers of the federal and the state government. yhe executive branch is headed by the oresident. there are two chambers of congress, the senate and the house of representatives. judicial power is exercised by the judicial branch (or judiciary), comprised of the supreme court and lower federal courts. the judiciary's function is to interpret the   constitution as well as the federal laws and regulations.