I also just noticed this:
I have never tinkered with these settings and I have no intention to, as I want to make sure that I follow the appropriate (EU) laws. However, the set currently seems inconsistent to me. Should the "wl_country_code" not also be "EU" instead of "US"? If so, (how) can I (safely) change that?
Also weird: OS X El Capitan's Wireless Diagnostics lists the country as FR while I don't live in France.
wl_country_code isn't used by the firmware. It's a temporary value that is usually generated by the webui, and then it gets copied to wl_0 and wl_1 instances for the two radios as settings are applied.