So in regards to blocking specific countries you will need to acquire the ip address range using 3rd party sites but for example if I was in another country and wanted to block the united states I could use code like this:
This code was generated using a 3rd party site (https://www.countryipblocks.net)
Once you have the code generated you can place it within your .htaccess file, I have included a link to more info regarding that if you are not familiar.
(ip address range in example is not complete due to character restrictions and does not work)
<Limit GET POST> deny from 126.96.36.199.0 allow from all </Limit>