This post (with reading material below) is meant, not to absolve Mahmoud Ahmadinejad from his delusional comments and periodic invective, but to inform that the history of U.S.-Iranian relations is more complex than its presented by the reflexive, anti-Iran politicians and pundits often frame the issue.
For Further Reading:
Military Action Against Iran
The 1953 U.S. Backed Coup in Iran
The U.S. and Iran
The U.S. and Regime Change in Iran
U.S. Military Involvement in Iran
Win One For The Gipper