'Fake news', which has been flagged as a threat to democracy, had little impact on the 2016 elections that saw Trump win the presidency, according to recent study. Researchers showed that the majority of Americans did not consume 'fake news' through social media or other mediums (only one in four saw at least one fake news site), although fringe supporters of Trump did consume quite a lot of fake news. The data gathered from a sample of 2,525 Americans reveals fake news made up only 6% of the news diet of deeply-conservative supporters of Trump and 1% of that of Hillary supporters.
Overall, I think it's safe to say the Russia poses as much as of threat to America as fake news does.
Sources:
https://www.dartmouth.edu/~nyhan/fake-news-2016.pdf
https://www.nytimes.com/2018/01/02/health/fake-news-conservative-liberal.html