Truth be told the president is a figure head position. His or her strength comes from the amount of (influence) they bring to the table. A president cannot write or pass laws for the most part. That is congress' role. He may conduct some executive orders. Therefore the real measure of a president is to gage how (effective) he or she is in accomplishing what (they) set out to achieve by getting others to execute their agenda.
Every country chooses it's own destiny. America attempts to control a nation's behavior by providing financial aid in various forms to those countries who act accordingly to our national interest. When they don't we either apply financial sanctions to cripple their economy or we use military threats/war.
This reward/punishment technique is the same policy used by both Republicans and Democrats. An outside nation cannot (truly change) the mindset of nations that hate one another.
"A man convinced against his will is of the same opinion still." Real change has to come from within the countries at war. They have to cultivate their own leaders for peace.