[AaronFriel]

Not a lawyer and would be interested to read a constitutional law journal on this.

I think the answer hinges on where the speech is considered to be, and whether the speaker is an American.

An Iranian national handing out leaflets in Washington, D.C. is protected speech by virtue of it occurring in the United States.

An American national posting on the internet is protected from United States government orders to censor their speech, regardless of where they post it, by virtue of their nationality.

Where it gets murky is: "Is an Iranian national posting on Facebook 'in America'? Does it depend on whether they make a comment in Iran or in the United States?"

That's the sort of hypothetical that a court might be keen to sidestep entirely and instead ask, "Is it constitutional for the US to order a US company (Facebook) to engage in non-viewpoint neutral censorship?"