The President of the United States of America's role was clear as stated by the founding fathers: veto or accept laws proposed by Congress and to appear at foreign events. In recent years, this job has been virtually effaced by corrupt executive orders even though the Constitution does not guarantee the President can execute orders. The President's job should be restricted to appearing at international events such as United Nations meetings and to veto laws only when he/she can provide an alternative (Article I of the Bill of Rights does not refute the idea of the President being required to provide another solution to a bill).
Sources: Bill of Rights, 12th Amendment, 20th Amendment, 22nd Amendment and 25th Amendment.