Does it really? I'm genuinely curious during what time period you think our government would've reacted differently. This got me thinking, how would people expect different countries to react to something like this?
By making that tweet he's impersonating a government agency and passing it off as an official document. If he hadn't posted that tweet I'm sure he wouldn't have anything to fear.
EDIT: I looked up the relevant law: False Impersonation of Federal Officer or Employee [0]. It doesn't seem he got anything of value, so it's unlikely he could be charged. Although I'd be surprised if he didn't at least receive a stern conversation from a government official.