“In paper based systems, you and other volunteers”

No, 99.99% of “you” go home and “trust the system” to some poll workers, many with major bias and incentives. Many of “you” don’t turn out to vote or are disenfranchised by simply living too far from the polling place or not being able to take time off work, when you could have just voted from your app.

Certain parties even rely on suppressing turnout. (Can you guess which party does that in USA? Hint: it’s the one that closed 1600 polling stations right after the Voting Rights Act got neutered, and then got mad about mail-in ballots ruining their carefully laid disenfranchisement plans during the pandemic.).

In fact, if you want the election to be “secured by multiple distrusting parties”, that is exactly what byzantine-fault-tolerant cryptographic protocols (which power many blockchains) are designed to do.

(how do you fix an error in the Merkle tree, even if everyone agrees it happened?). Even if you have an extremely corrupt county, that doesn't generally matter in the grand scheme of things; and its extremely unlikely, as any citizen in that county can stop the corruption by simply participating in the process themselves.

You are literally arguing from a double standard. In a paper election, somehow “any citizen” by themselves can stop the corruption… by simply participating in the process.” Yeah sure one guy exposes the entire corrupt county, with no ability to prove how anyone voted, why didn’t a single Belarussian and Venezuelan think of that? LOL” And on the other hand, when you have tons of anonymous irrefutable proofs by participants submitted publicly, you throw up your hands and say “what can we do to fix the merkle tree, even if we all knew it was corrupt?” The point of the trre is to catch errors, prove them and publish the proofs widely. As a society, you then have the proof nexessary to fix errors the same way you’d normally do it — by identifying the corrupt districts, and having a recount or revote just there. And bringing those responsible for tampering to justice.

If you stop conflating all the things and unpack them, you’ll see that adding cryptography makes things strictly better:

1. You have more chances to catch if there have been extra votes cast because the private keys are coming from tokens handed out at registration. In a paper election you might have corruption at registration AND all manner of ballot stuffing later too.

2. Everyone can check their vote and report a discrepancy. Not just the volunteers at the polling places. And all because they can prove how they voted and do it anonymously!

3. Everyone can see exactly which districts are corrupt in giving out fake voter registrations, and where there’s smoke, there’s fire. They can do an audit and guess what, the cryptographic signatures are helpful for creating a PROVABLE trail that implicates the system.

4. The attack surface reduces to pretty much just the voter registration sybil attacks. Eliminating a whole class of problems on actual election day.

5. The results are reported to everyone reliably and quickly, or even in real-time (though the latter is “too good” because it might affect how later voters vote).

There’s practically not a single problem that adding cryptography creates, which wasn’t already present in the paper system. And you know all this because if you honestly asked yourself whether dictators, who want sham elections, would want to do their next election with cryptographic signatures and merkle trees or not — what would be your answer? Be honest. And think about what that means for your argument.