To display the country codes requires that the following line is configured in the awstats configuration file for each website in /etc/awstats:
DNSLookup=1
The default configuration is DNSLookup=2.
The drawback to turning on the country codes is that it makes awstats processing take much longer. With DNSLookup=1 it can take several minutes for the stats to completely process.
There is a secondary, more complex way to enable country codes without the added time for statistics processing. This method involves enabling awstats plugins (GeoIP or GeoIPfree) that you would have to install. More information on this method can be found at the AWStats website at:
http://awstats.sourceforge.net/docs/awstats_contrib.html