The history between the US and Iran is one that has been filled with deception and mistrust. While some of that deception and mistrust is justified, most of it is just suspicion and political opinion.
The first conflict between the US and Iran was very severe. In 1951 the United States and Great Brittan invaded Iran to take the dictator Mohammad Mossadegh out of power. This came after Mossadegh had nationalized Iranian Oil prohibiting its export to the United States and to other world powers. The invasion was successful and Mossadegh was arrested. After that the United States helped Iran rebuild.
We had very good relations with Iran until 1978 when the Iranian Revolution took place. This turned Iran from a monarchy to an Islamic Republic. Relations for the next year were tedious at best and then in 1979 Iranian students attacked the US embassy in Iran. They took 52 diplomats hostage. They held the hostages for 444 days. When they were finally released, relations between the United States and Iran were changed forever.
For the next 20 years tensions between the United States and Iran steadily grew and intensified. They finally came to a head in 2002 when the United States accused Iran of illegal Nuclear Proliferation. The US then announced several stipulations that Iran had to comply with in order to maintain good relations with the United States. Iran did not comply with the United States' demands.
In 2006 the United States imposed economic sanctions against many international businesses located in Iran. In 2007 the United Nations followed the US and imposed sanctions with an even more devastating effect. In 2008 the US House of Representatives proposed a plan to blockade the Strait of Hormuz. The Strait of Hormuz is the only waterway linking the Persian Gulf with the rest of the world, and Iran's only way to ship goods by sea. This action would seriously hurt Iran's economic status.
However, the United States and Iran did agree to take part in a peace summit in Baghdad. This is the first formal step toward peace between the United States and Iran in decades. However this step was overlooked greatly in the wake of the 2009 Iranian Presidential Elections. The future between the US and Iran is murky and unclear, but if history can tell us anything it is that peace is always possible even in the most grim of circumstances.