monthly updated GeoIP db is available for free for non-commercial use also from
and for commercial use a more frequently updated IP db from maxmind as well.
instead of banning all NON-US countries - i have setup a large iptables list blocking C/B or even A networks ( specially china ) if i encounter a hack attempt.
normal is about one daily hack attempt on a server ...
my first one started before my domain was fully setup - that helped me to strengthen the security.
NO password login - only serverkey access via ssh
if blocking ALL NON-US access - pls keep in mind that you also deny access to all US abroad - there are MILLIONS of US citizen permanently or tgemporarily living abroad / overseas, it also blocks all US on travel, on vacation - including yourself when traveling ...