"Why would a mentally ill 20 year old with a loving family, including a Jewish father, pretend to be an Islamic extremist online and engage with other extremists to discuss potential attacks?" Mr Shorstein wrote in a sentencing memorandum.
Goldberg was living at his parents' Jacksonville home in 2015 when he used online aliases including Perth-based Australian Islamic State terror group member "Australi Witness" and "Australian radical Muslim" Junaid Thorne.
He told an undercover FBI source "he was attempting to get an individual in Melbourne" to carry out a terror attack.
Goldberg also claimed responsibility for inspiring a deadly terror attack on a controversial Muhammad cartoon drawing competition in Texas, and encouraged the FBI source to build a bomb and commit a terror attack at a September 11 memorial event attended by firefighters in Kansas City.
Mr Shorstein said Goldberg wanted to be a journalist.
He pursued his plan by reaching out to Australian journalists at Fairfax and SBS and Perth-based reporters from 9 News, Channel 7 and Ten News.
"He planned to discover and acquaint himself with real extremists over the internet, get them to reveal plans of attacks, memorialise them with screenshots, and then expose them and write about them to become a journalist," Mr Shorstein wrote.
"While this sounds like a fantastical idea, he actually executed this plan well and received positive feedback from many established journalists."
Aliases Goldberg used to "further his plan to become a journalist, to discuss movies" or "to stir up debate and 'chaos' on" Twitter, Reddit, IMDB, Facebook and other social media websites included: Junaid Thorne, an Australian radical Muslim who was used to attract real terrorists; Amina Blackberry, an African-American conservative woman living in Washington, DC; Michael Slay, a neo-Nazi calling for the extermination of white people; Emily Americana, a Samoan woman in Alaska who does not like fat people or Europeans; Nuke Europe, a European Jewish guy who experienced anti-Semitism throughout Europe; and Flappy Bird, a far left woman who promoted gender issues on behalf of women and transgender people.