Counties did that for most of history; but as the number of voters increased, the system became terribly inadequate and time-consuming. The old voting machines were introduced (which is a card punch system behind the machine, and those cards are run through card processors after the vote): THAT system is probably better, EXCEPT FOR POSSIBLE HANGING CHADS (Bush v Gore). The above link looks like attempted interference BEFORE the election, by accessing state voter registration data (which the Russians didn't realize comes from each COUNTY and is provided to the state) and a LOT of that is manual data which people in certain states argued was manually changed in that state to stop certain voters [Dems] from voting and that wasn't the Russians, it was Republicans. Trump claims that manual voter fraud enabled "millions" of undocumented aliens to vote for Clinton but that claim has been waived off as ridiculous.
Edit: Sorry, I was typing this on my iPhone as @DigitalChaos was entering his response.