Acting US Attorney for New Jersey Alina Habba announced the grand jury indictment of the Democrat in a post on X.
"While people are free to express their views for or against particular policies, they must not do so in a manner that endangers law enforcement and the communities those officers serve," Habba said.
In a statement, McIver said the charges amounted to the Trump administration trying to scare her.
"The facts of this case will prove I was simply doing my job and will expose these proceedings for what they are: a brazen attempt at political intimidation," she said.
McIver, was charged in a complaint by Habba last month with two assault charges stemming from the May 9 visit to Newark's Delaney Hall — a 1000-bed, privately owned facility that Immigration and Customs Enforcement uses as a detention centre.
The indictment includes three counts of assaulting, resisting, impeding and interfering with federal officials.
Habba said two of the counts carry a maximum sentence of up to eight years in prison. A third has a maximum sentence of one year.
McIver's lawyer, former US Attorney for New Jersey Paul Fishman, said in a statement that they would challenge the allegations "head-on" in court.
"The legal process will expose this prosecution for what it truly is -- political retaliation against a dedicated public servant who refuses to shy away from her oversight responsibilities," Fishman said.
The indictment is the latest development in a legal-political drama that has seen President Donald Trump's administration take Democratic officials from New Jersey's largest city to court, tapping into the president's immigration crackdown and Democrats' efforts to respond.
The prosecution of McIver is a rare federal criminal case against a sitting member of Congress for allegations other than fraud or corruption.
At the same visit that resulted in McIver's charges, Newark Mayor Ras Baraka was arrested on a trespassing charge, which was later dropped. Baraka is suing Habba over what he said was a malicious prosecution.
