Defamation only applies when the lie is causing harm to a specific person. It's just a special case of lying. As far as I'm aware, there's no existing law in the US that would penalize lies (from the media or otherwise) in general.

I don't see this as a particularly problematic idea. Assuming a high burden of proof, why shouldn't a deliberate hoax from a news organization be treated as a kind of fraud or "malpractice"?

An alternate implementation would be for the FCC to regulate this and unilaterally issue fines for broadcasting fake news, but that seems ripe for abuse and more against the spirit of 1A.

Instead, I like the idea that anyone (either the state or a private citizen) could sue any news outlet for publication of a hoax; not necessarily claiming any direct or personal harm caused, but just to defend the principle of truth. The process would be as fair as possible — requiring evidence of willful intent to the standards of a court of law, allowing appeals all the way up to the Supreme Court, etc. — but in return the consequences would actually have teeth. Offhand, I'd say fines roughly comparable to securities fraud and a journalistic equivalent of disbarment for individuals responsible.

Yeah, and even when the lie is causing harm to a specific person, the U.S. media are mostly immune from libel lawsuits when that person is a public figure like a politician or business owner they're opposed to. Also when they turn that person into a public figure via their campaign of lying, I believe.