It had a YUGE effect. - $100,000/$2,600,000,000 = 0.004%
Not sure why putting up money spent somehow discounts any possible affect from fake facebook stories put up by Russians.......I would think the number of views, shares, etc. would be a more relevant stat to try and determine any possible influence. I agree with @kc78 that to think that it didn't affect votes is completely crazy, I also had a few friends that said they were on the fence get duped by known fake articles. Let's not forget, this was the first election in which more people were voting AGAINST the other person, rather than voting FOR their person (and this was in September, so in all reality these numbers went up)........and it was far more prevalent among those voting for Trump (53% voting against Clinton/46% voting for Trump).
With that said, I think it would be impossible to determine if any of that actually changed the election results.......there's far too many unknown variables.