The Duke of Sussex sparked controversy when he told podcast host Dax Shepard that he thought the amendment to the Constitution, which protects basic rights like free speech, was “bonkers”.
And commentators on the right-wing channel, which is owned by Rupert Murdoch, were quick to heap scorn on Harry.
Conservative commentator Jesse Watters mocked Harry for complaining about the press more than Donald Trump.
“Well if he thinks the First Amendment is bonkers, wait till he hears about the Second one. This guy complains about the press more than Donald Trump.
“Is he a member of the Royal family? I didn’t think Royals were allowed to complain. Nobody else in his family complains about anything except the climate, I guess.”
Watch: Dax Shepard recalls infamous Conan interview and being ‘banned from that show for some years’
Watters then suggested that Harry should “see a shrink” and even compared him to Dr Anthony Fauci.
“Why is he talking so much? Keep it inside a little bit. See a shrink. Don’t do every interview. He’s like Fauci.”
Another host, Sean Hannity, said: “Harry, we really don’t need you coming from England to give us lectures on the First Amendment.
“And if you can’t understand the importance of free expression and the importance of constitutional principles that allow for a free exchange of ideas and opinions that make America the greatest country on Earth then maybe it’s time for you to move to a place more compatible with your restrictive ideas.”
Hannity also said that the same First Amendment “allowed you and your wife to trash your own family in the Oprah Winfrey interview. You and Meghan were allowed to accuse your family of racism.”
Greg Gutfeld also took a shot at Harry, and wife Meghan Markle.
“The guy claims that he hates the press and paparazzi. So I know what I’ll do. I’ll move to Hollywood with a fame-hungry actress,” he said.
“That is not fleeing Paparazzi. They know exactly what they’re doing.”
Harry told Shepard on his podcast that he had been shocked by the “media feeding frenzy” around he and Meghan after they moved to a luxurious mansion in Beverly Hills.
“I don’t want to start going down the First Amendment route because that’s a huge subject and one which I don’t understand because I’ve only been here a short time,” he said.
“But, you can find a loophole in anything. You can capitalise or exploit what’s not said rather than uphold what is said.”
The First Amendment protects a string of basic freedoms under the US Constitution, including freedom of speech, freedom of religion, freedom of the press, the right to assemble, and the right to petition the government.
Fox News host Laura Ingraham also tweeted, “Don’t let the doorknob hit you, Windsor.”
Ben Domenech, the publisher of The Federalist, also blasted Harry when he appeared as a guest on Fox News.
“The reality is that Prince Harry should be tarred and feathered and sent back to his grandma,” Domenech said.
“He is not someone who appreciates anything that makes America great.”
And he added: “The royals are yet another decaying Western institution – morally and financially bankrupt. I think we ought to dump (Prince Harry) into Boston Harbour along with all the tea.”
Watch: Prince Harry should be 'tarred, feathered, sent back' to Britain - Domenech