For Montesquieu, despotism was one of the worst threats for a government. He pointed separation of powers as the best way to prevent it, in which legislative, executive and judicial power was excercised by different bodies of government, and these bodies were ruled by supreme law.
The system of checks and balances is very important for the U.S. government, since it was developed to assure that neither of the government's branches would empower too much. The writers of the U.S. Constitution developed a system that divides power between legislative, executive and judicial, and incorporates several limits and controls on the powers of every branch.