Thank you for your response!

I see. It's weird that I can't use a column that's right there in the database and would uniquely identify any entry.

When I checked the Nginx documentation, I saw this:
"$geoip_region
two-symbol country region code (region, territory, state, province, federal land and the like), for example, “48”, “DC”."
That should be the "subdivision_1_iso_code" in the database.
Meanwhile, when I logged my activity, I saw the name of the region (subdivision_1_name) in the logs and when I changed to "$geoip_region_name" nothing was logged.