Earlier quoted context omitted.
There are a lot of countries.
there are about 250 or so. it's not hard to make a complete list and drop the few undesired ones.
Going from a whitelist to a blacklist is hard because you need to either individually vet every country and decide if they're ok, or you need to just assume a lot of countries are ok.
Going from a blacklist to a whitelist is obviously trivial.