Explain Like I'm 5 (ELI5)

I'd expect the state to have a list of all its citizens and their basic personal info (age) which could be used to determine their eligibility for voting. In my country, we get a "invitation" to the vote, with your voter station and info on how to change it.

Instead, I'm seeing posts about USA's "voter rolls", which are sometimes purged, which prevents people from voting. Isn't this an attack on the voting system and democracy itself?

So why doesn't USA have a list of voters? Are they stupid?