Not every denial of a U.S. visa application for an Iranian citizen is related to Trump's travel ban. Some applicants simply fail to pass the extensive background checks in place well before Trump took office. These background checks apply to visa applicants from all over the world. Whether justly or not, applicants from the Middle East, in particular Iran, are scrutinized more heavily.
One of the reasons most cited in recent visa denials is INA Section 212(a)(3)(B) – inadmissiblity due to terrorist activities https://uscode.house.gov/view.xhtml?req=granuleid%3AUSC-prelim-title8-section1182&num=0&edition=prelim. Clearly the vast majority of these denials are in error and the net set is far too wide. The State Department's reasoning is probably based on the applicant's employment and/or educational background.
Earlier in 2019, the United States declared the Iranian Revolutionary Guard Corps (IRGC) a terrorist organization https://www.state.gov/designation-of-the-islamic-revolutionary-guard-corps/. This includes Sepah, Basij, and all other subsidiaries and formations. Unfortunately this also includes almost half of the Iranian economy.
Persons who even unwittingly worked or studied in any of the IRGC funded organizations, including schools, hospitals, and otherwise benign places may be subject to the terror ban. Even if their involvement with the Guard was before the terrorist designation in April 2019, though legally mind-spinning – the ban still applies. Furthermore, the mandatory military service in the Islamic Republic, if served with the Guard, will trigger this bar. Yes not fair – but that's a different conversation.
Our office has extensive experience in this area. Please contact us to schedule a consultation with one of our attorneys.