The US designed a system to interfere in foreign elections by changing vote totals in the machines.
The irony of a special prosecutor investigation into Russia influencing a US election just got richer.
See, and here is where the technical guy in me goes "Huh????!"
There is not one single type of 'machine' used to tabulate votes. There is not one kind of software.
In order to affect vote totals, you must penetrate a given machine (and each type requires a different method of penetration), and then you have to adjust the vote totals in the SOFTWARE, and HERE is where it becomes nigh-impossible.
See, the totals may be stored on a db. Which one? What security controls? Those numbers may be encrypted. How? Maybe the numbers are sent to a flat file. Where do the numbers reside? How can you know where to look? Did you leave out 'decoy' columns which look like vote numbers but is never actually used? There is so much variation, and variability, that I suspect it would be yeomans work to do this hack on a single country.... much less the 50 mini-countries that are our United States.
I suppose an advanced AI system could figure it out, but I don't think AI is that advanced yet.