Do Apple WiFi drivers have a problem with Asus Routers?
No, it is not so that Apple devices somehow cannot read the country code for North America.
Some WiFi devices comes with a settable country code - i.e. often you can access a configuration page from the router and set the country code to match where you are. For some vendors the country code can be changed with firmware updates. Also it is possible that you received your router via parallel import from somewhere else (China or similar) - and that it doesn't have the NA country code because of this.