An expunged conviction is still factually something that happened. Under the First Amendment, it's never libel to state a true statement of fact. If the matter is of public concern, the plaintiff in any defamation action must prove that the statement was false. And if the plaintiff is a public figure knowledge of falsity or reckless disregard for truth must be proven. In addition to the robust First Amendment protection of free speech, there is 230 of the CDA, the federal Speech Act barring enforcement of most foreign libel judgments and local anti-SLAPP laws. I really can't see any ground for any legal action in the US that would be consistent with the First Amendment. Also courts have held that the First Amendment does not permit liability for republishing facts of old expunged convictions.