There are quite a few people and organisations analysing social media accounts. They have, on occasion, exposed botnets, or networks of fake accounts that are manually run.
I know of a few here in Germany, and I have no doubt that they would gleefully publish any US government networks they come across. And with the extreme polarisation in the US, there should be plenty of people or publications on either side to do the same.
The fact that, as far as I can tell, these tend not to be bots but manually-run fake accounts might point to an explanation of the relative lack of such activity: it might just be too expensive. And when it comes to networks targeting other countries, every country that isn't natively English- or Spanish-speaking is relatively save because you aren't going to find hundreds of Americans speaking Russian willing to work for low wages and reliably keep quiet about it.
That, of course, is in addition to the obvious reason that democratic countries by their very nature just don't do stuff like that. But I have a hunch the ever-cynical crowd here would take offence at the idea that some countries and governments sometimes don't behave in the worst possible way.