Nearly 21 million voting-age U.S. citizens do not have a current (non-expired) driver’s license. Just under 9%, or 20.76 million people, who are U.S. citizens aged 18 or older do not have a non-expired driver’s license. Another 12% (28.6 million) have a non-expired license, but it does not have both their current address and current name.

Additionally, just over 1% of adult U.S. citizens do not have any form of government-issued photo identification, which amounts to nearly 2.6 million people.[1]

[1] https://cdce.umd.edu/sites/cdce.umd.edu/files/pubs/Voter%20I...

In many states these are available without proof of citizenship. When people say proof of citizenship they usually mean a passport or REALID.

In the US, a driver license isn't a proof of citizenship. Also, state IDs are not accepted by federal agencies, so it probably wouldn't work as proof of citizenship on federal elections.