US-born Muslim convert Marzieh Hashemi was arrested at St. Louis Lambert International Airport on January 13 under a law allowing authorities to detain people suspected of being potential witnesses in criminal cases.
Back in Tehran after being released, she said Saturday the "material witness law" has been "used systematically to target mostly Muslims in America for over two decades".
"I was imprisoned and treated like a criminal under this law without a single charge," she said at a press conference in Tehran, adding that the law uses "false, flimsy or irrelevant evidence to secure arrest warrants against Muslims."
Hashemi, who changed her name from Melanie Franklin after converting to Islam, works as an anchor for Iran's English-language television station Press TV.
Hashemi had been in the US to visit her ill brother and other family members as well as working on an "independent documentary project" on police brutality against African-Americans, she said.
She was unable to give specific details on her imprisonment, for legal reasons, but called it a "fishing expedition" with no credible cause or charge.
A US court said last month her testimony was required over an unspecified case, but that she was not accused of a crime.
Iran's foreign ministry also summoned the Swiss ambassador to Tehran, who represents American interests in the Islamic republic as the two countries broke off relations following the 1979 Islamic revolution.
Iran's Foreign Minister Javad Zarif accused the US of violating the civil rights of black people, slamming Hashemi's arrest as a "political" move that "tramples on freedom of speech".