Imperial presidency term was used by Arthur M. Schlesinger,
Jr. to describe the presidency of the United States. Schlesinger wrote the book
The Presidency because of his concerns that US presidency was uncontrollable
and according to him, exceeded the constitutional limit. This book is where the
term imperial presidency became notable.
The population of the state decreased
They all studied the social contract.
The constitution of the United States set up a set of checks and balances among the three branches of government. The Legislative, Executive and Judicial powers constitute the structure of the american government, and they have power to check each other's way of work.
One example of the check and balance system is that the Supreme court of the United States may check congress by declaring a law passed by this one as unconstitutional. This is a clear check limit used against the legislative power, that is the congress. But on the other hand, the power is balanced because the members of the Supreme Court are appointed by the President of the country (the Executive power), and to be appointed they have to be approved by the Congress.