The following is the March 26, 2018 Congressional Research Service report, Iran: Politics, Human Rights, and U.S. Policy.
From the Report:
Since the Islamic Revolution in Iran in 1979, the United States and Iran have been broadly at odds. During the 1980s and 1990s, U.S. officials identified Iran’s support for militant Middle East groups as the primary threat posed by Iran to U.S. interests and allies. Iran’s nuclear program took precedence in U.S. policy after 2002 as the potential for Iran to develop a nuclear weapon increased. Beginning in 2010, the United States orchestrated broad international economic pressure on Iran to persuade it to agree to strict limits on the program—pressure that contributed to the June 2013 election of the relatively moderate Hassan Rouhani as president of Iran and the eventual negotiation of a “Joint Comprehensive Plan of Action” (JCPOA). The JCPOA, which took effect in January 2016, exchanged broad sanctions relief for temporary limits on Iran’s nuclear program. The JCPOA reduced the potential threat from Iran’s nuclear program, but did not address the full range of threats posed by Iran, including from its ballistic missile program; its regional influence and support for armed factions; its conventional military programs; and its human rights abuses.
Some experts and U.S. officials have asserted that the threat posed by Iran stems from the nature and ideology of Iran’s regime. Whereas hardliners continue to control the state institutions that are responsible…