So I was pondering this question as well.
I strongly feel against Russia ( or any other country for that matter ) deciding the next election in the US ( or we should be allowed to meddle in their elections as well ... ). Think this through. Russia could use their leverage on a candidate then to trigger our military to do their bidding, or to self destruct or to give Alaska away for free.
So if something like steemit could be used as a means to verify your nationality ( think how root certificates, and https work on the web ) that would be helpful.
No, I don't want to add a limitation on the first amendment to the American constitution "freedom of speech and expression". Say what you want !
I also don't want to block foreign comments. All I would like to see is some way to give visibility if the comment comes from an american citizen or not. So a binary flag basically..
I agree that this has been tried in the past by foreign governments ( and kingdoms ) however in the past you would have to fly a plane over all cities and drop leaflets with political information. Now you have the Internet ...