What TequilaMockingbird points out about what "we did" in Iran is true.
I also feel that Iran and Vietnam have similar parallels.
After the end of WWII and the defeat of the Japanese, it was decided that Vietnam was to be "returned" to it's status as a French colony. Ho Chi Minh had petitioned the U.S. to force the French to give Vietnam it's independence, and we declined to intervene. It's possible that could have turned them from civil war, and the north turning communist.
I do feel that overall, in an international sense, the U.S. is largely a "good country". Leaving out nations that are not major international players, like Canada, Sweden, and Iceland etc., we're possibly the "best" out of all the ones that have ever had such global reach and power. Overall, we've done far more good than harm, IMO. (Just ask a Nazi or the Imperial Japanese
)
However, I do think that our "Win at all costs" strategy when it comes to pulling the puppet strings in other lands is our greatest "external" sin as a nation. We only seem to support true democracy, human rights, and freedom when we're reasonably sure of the outcome. A U.S. apologist could say that it was driven out of fear of losing to the Sino/Soviet Communist machine (a.k.a. "Domino Theory"), but one can easily see that it extended much further back to the "Banana Republic" era in South America well before the October Revolution in 1917 put Communism on the map.
Aside from slavery, it's going to be the single most greatest stain on our history.
Despite whatever historical details may be in error, I agree with the essence of Dmack_901's analysis.
While what we've done in Iran is certainly a major contribution to Islamic hatred of the West, and the U.S. in particular, the true roots of the conflict between radical Islam and the West date all the way back to the days when the Roman empire squared off against Persia, the Crusades in the middle-ages, followed by the defeat of the Ottoman Empire and subsequent British and European Colonialism, to the support for Israel in 1948, and up to our involvements in the regions in current times. The U.S. is an inheritor to that entire 2000 year long legacy. We view that litany as discreet events in distant history, and not as part in any larger pattern of conflict. The Islamists do not. To them it is all one epic struggle. It is impossible to make diplomatic amends for things that happened between other 1000 years ago or more. Even if we could, they would not care.
Understanding that fact is key.
If we waited another ten or twenty years for the Iranian hatred for our backing the Shah to fade, or even a hundred for our support of Israel to diminish in their minds, it would still be there. Look at France, and their recent riots. Even if we took the greatest "spread yer legs, and show yer (yellow) belly" diplomatic stance the world has ever seen toward the Islamists, they would not go away.
If you think I'm kidding, look for the statements by the leaders of our enemies to their public audiences. The word "Crusade" comes up quite often. To them it's a loaded, hot-button, term, even almost 1000 years later!
I believe that even if the U.S. had a time machine and managed to divorce itself from British colonialism, publicly opposed the creation of Israel, and had never meddled in Iran or Iraq, we would still be on the Islamist's "hit list". At best, I think such a revision of history would have only bought us a few decades of breathing room.
As the default "leader" of Western Civilization both economically, and culturally, and the last identifiable possessor of the Zeitgeist (currently up for grabs…), I believe that the U.S. would inevitably be a target for Islamo-Fascisim. And quite possibly, that would be a united Islamist front, in possession of a modern nuclear arsenal, bio-weapons, robotics, killer nanotechnology, or God knows what else.
