America had established itself as a Super Power after, the World war II in 1945. The economical condition of many of the countries had fell down for this war. In that time, America had planned to brought under it to many country heads of middle east by means of monetary helping.
A big oil well has discovered by a company of Britain in that time. The former Iranian PM Mosaddegh had nationalized all the oil tanks in 1952. This was unhappy to England. Because, in that time , that Britain Company has the owner of all the oil wells of Iran. So, Britain had thrown out the PM of Iran by the help of America.
The real chief of the country then, was King Mohammad Raja Saha. He again and again changed the prime ministers of the country in the direction of America. So, the publics of Iran had protested against Saha. Ayatollah Khamenei had taken leadership for this protest.
Raja Shah had run away to America in 1979. Then peoples of Iran had nominated Khamenei as their leader. Khamenei had shut down all the American companies situated in Iran. America had got angry with this.
Iraqi ruler Saddam Hussain attacked Iran in 1980. America had given full support to him. This was the starting of rivalry between America and Iran. Many of the countries from middle east has accepted the mastership of America except Iran till now.