All things that are already registered in the government's basic citizen administration (or whatever it's called in your country). Deaths and moving to a new address are both things you are required to register with the government ASAP.

This actually sounds like a science fiction to me. You obviously don't realize how antiquated and disconnected governmental bureaucracy is here in the U.S.

Very few systems can access data gathered by other systems. Job applications and other processes often require "background checks" to verify our identity by cross referencing several disparate databases and searching local and federal data for criminal histories, evidence of name change, etc. Meaning before someone will trust you with employment or a loan, they will pay a service to verify who you are because it's such a difficult process to do.

The affidavit vote counting process is essentially doing that background check on each voter to verify their identity and eligibility to vote. And the Mississippi count at issue here is happening in one of the poorest, most understaffed, and most technology unadvanced states in the country.