There really isn't a good case to be made for electronic voting at all. Paper is much simpler, more reliable and has none of these issues.
A typical U.S. ballot may have 20 or 30 issues on it.
Even if one assumed that all other factors were equal (they aren't), even the raw counting might be expected to consume 20 or 30 times as much time.
We vote on a LOT of things here, and it becomes quite complicated.
A U.S. voter may well be voting on issues related to the sewer district, and the school district, and the library district, and the city council, and (this is important) those various districts might be overlapping or even disjoint. Just because both Bob and Alice are in Sewer District 5 doesn't mean they're both in Road District A. Far from it.
It takes time just to ensure that everyone has been given the proper ballot, much less count and combine the figures from various polling stations (Sewer District 5 may cover multiple polling stations, as may Road District A, but they may not be, and probably aren't the same stations).
It's a mess, granted, but we prefer voting on stuff rather than electing a council or MP who takes care of everything for us.
There are many races to vote in at the national, state, and local level. Besides President, every ballot would have included house rep and 2/3 of states had a Senate race. Then add state governor, house rep, and senate which often align on the same cycle. Most states also elect attorney general, treasurer, education and several other statewide executive offices. Some states elect state supreme court judges. Then there can be mayor, city council, school board, port commissioner, and other local offices, although many states align these to non presidential election years. Then there are states like California that always have several initiatives.
In practice, you are looking at dozens of races on this year's general election ballot in many states. Counting all those on paper would be time consuming and possibly less accurate than using an optical scan counter.
The moment you introduce any kind of electronic system into the voting or counting process nobody can understand it all anymore, there's a million lines of code and billions of transistors, nobody can validate the entire thing and even if they could, you couldn't, you'd have to trust the people can.
In my county, paper ballots are used (used to use electronic booths) and the form is printed in English, Spanish, Korean, and Vietnamese. Hypothetically an electronic ballot has no issues with localizing to an infinite number of languages without regards to costs of printing out separate ballots. Electronic voting isn't impeded by the restrictions of paper. It could have rich media, sound, videos, etc.
Accessibility is another potential advantage. Right now with paper ballots the expected procedure for voting as a person who is unable to use the ballot is to have a family member fill it out for them. Electronic voting means that you can make accommodations for all sorts of disabilities and special needs while still allowing the person to vote without the need for a proxy.
Electronic voting could be more convenient than in person paper ballots. Hypothetically if a person could vote online on their phone, the process would be more convenient and more people may vote. It also makes it easier to vote for people that are traditionally disenfranchised due to time constraints of voting in person (they can't afford to go to the polls, even if there exists laws that require employers to allow for time to go vote on election day). It also limits avenues for voter intimidation.
Finally, electronic voting would (hypothetically) be instantaneous and accurate. It isn't dependent on humans for counting. There isn't really a potential for 'hanging chad' incidents. We'd know the victors of an election as soon as polls close.
The issue is unfortunately all of these advantages don't really outweigh the issues that we don't have good solutions for (yet, or maybe ever).
Electronic voting isn't tamper proof. Having open source voting software doesn't really help verify that the software that you say is running is what actually is running. If it is exploited, it is much easier to tamper with electronic votes than it is paper ones. If it is online, that opens it up to even larger issues of exploitation.
There's no way to verify that what you intend to vote for is how you actually voted according to the machine. With a paper ballot there is tangible proof of how you voted, while that doesn't exist on a purely electronic vote.
Paper ballots have their own set of issues, but they are manageable compared to the current limitations we have for dealing with electronic voting.
We're basically doing some degree of electronic voting with the machines that count the paper ballots anyway. And with the introduction of large-scale mail-in ballots, the argument against electronic voting is starting to fall apart.
Obviously I defer to the experts in the field for what is and isn't possible, but something about it scratches at the back of my mind...