1.Many an Islamic radical still sees the revolutionary activities abroad, export of the Islamic revolution as the basis of their country's self-identification and the source of legitimacy for their governance. Such a vision prompts Iran to support the Hezbolla movement in the Southern Lebanon and to block the Middle East peace settlement. That sort of activities makes the United States to blame Iran of supporting the international terrorism and, consequently, to define its status of "derelict" in the American political lexicon.
2.The United States pursues the pressure policy towards Iran in coordination with the European Union, and asks Russia to stop cooperation with Iran in developing nuclear technologies. Washington still suspects Iran of developing nuclear weapons, on the premises that to possess such weapons would have served the Iranian security interests. The United States agues, that it would have been  economically expedient and diminished the danger of collision with the nuclear armed Israel.
3.The current US administration is unlikely to change its super-tough line on Iran. Yet it is clear, that the United States will have to make a choice: either to develop the crisis of the Iraqi sort, or to normalize the relations with Iran, that has become rather complicated affair after the government change in Iran and changes in the neighboring countries (occupation of Iraq, instability in Afghanistan, the Russian Federation's active position in the region, etc.).
4.The key point in the Iran-US relations is the Iranian nuclear program. Washington would spare no efforts to not allow Teheran to obtain the nuclear weapons. These efforts might be successful, if Iran would prove the peaceful purposes of its program, but they might as well bring no results, in which case the United States would have to build up relations with the nuclear Iran.
5.It is still hard to assume, that America has already prepared to cross out the fifteen years of its domination in the Persian Gulf from history and to concede its role to the regional powers. Such a turn might be possible, only if there appeared a new wave of an isolationism in the American foreign policy and the US retreat from the positions won in the Cold War. There seems no indications of such a turn in the American policy, hence, the crisis in the US-Iran relations would go on.