One must be registered to vote. In order to register your background is vetted on whether you are qualified to vote (ie. a citizen). With ballots your name, address, and signature are supposed to be verified before the vote is counted. In order to vote, until recently, you had to provide your state issued ID card/driver's license prior to filling out a ballot. In 2016 only 32 states still require voter ID to vote. After Trump was elected, that narrowed down to 8 states.I've never had to provide proof of citizenship to vote. Is that a thing in America, you need to show up with your passport?
As of now there are several states that just send out mail-in ballots to every address and don't give a fuck who fills out and returns the ballots. It's why states like California love illegals. Gotta get the results the machine wants.