Only HI requires firearms to be registered in the USA.
And the last research on it, it's around 1/3 of the population.
https://www.pewresearch.org/social-trends/2017/06/22/the-demographics-of-gun-ownership/
That's from 2017, before COVID and trump really amping shit to the max. That 33% thinking about getting a firearm, many of them have. I'd say we're probably around %45 at this point. Many on the left have armed themselves since trump and COVID.