Thanks to the Mueller Report, we know that the IRA exposed 126 million Americans on Facebook to Russian-backed propaganda during the 2016 US presidential election. The group attempted to use disinformation to sway the 2018 midterm elections, too. US Cyber Command took the IRA offline on the day of the elections, and the Department of Justice later stated that foreign meddling had no impact on the outcome.
"While today's action only targets Russian actors, the U.S. Government is safeguarding our democratic processes from adversaries — primarily Russia, Iran, and China — that may be seeking to influence the upcoming 2020 elections," the Treasury said in a press release.
This isn't the first time the US has imposed sanctions on Russian nationals, and it's hard to say if the move will really change anything. It may be more symbolic than practical. Hopefully, the efforts do help safeguard the upcoming 2020 election, which is already at risk of being hacked and swayed by disinformation campaigns.