You've already found the best documentation page, although it doesn't specifically address the MX65W (which doesn't show a dedicated 'Radio Settings' page).
You can find the Country/Region for the MX65W by enabling at least one SSID on the MX65W (Security appliance > Wireless settings) and then scroll to the bottom of the page. If there's a conflict, you should see the warning and have the ability to request the change (based on the rules outlined in the documentation page you linked).
I suspect that once you complete the change, you will be able to disable the SSID again.
This might be a situation best left to a Case with Meraki support though.