There is no central id system in the US. There are several things that are close to a national id, like social security numbers, but they are also explicitly not allowed to be used as an id. There’s a very long history of US citizens opposing the creation of any sort of national registry.

States have id systems, but they still require a person to manually register for them. There’s limited interaction between states, so it’s possible to appear as a citizen of two states simultaneously, this is solved with eventual consistency and fraud charges for those who abuse it.

It’s getting better in some states, where they can update your voting registration when you change your address. Voting rolls are managed at the city and township level where they generally don’t have the resources to properly integrate data, which leads to outdated lists where a one bedroom apartment may have 10 different voters registered that lived there at one point. There’s no great way of knowing who the legitimate voters are, and who should be purged as they are no longer eligible to vote there.

There is a need to do some cleaning of the voter rolls, as accurate ones make planning easier. Printing a ballot for each name is wasteful if you know 20% of the names aren’t valid, but running out of ballots is unacceptable. Purging people who haven’t voted in say 20 years can reduce the number of bad names, but it will almost definitely affect a few people that haven’t moved and haven’t voted in 20 years. The attack on democracy is more theoretical than practical, that a person is going to suddenly start voting after not doing it for so long.