Blocking high level domains on email

I’m curious as to why none of the spam blockers that I have seen allow you to categorically block an entire high-level domain. For example, I know no one in japan and have no reason to expect a ligitimate email from anyone with an ending of .jp. I can set up a rule to filter out those, but that is cumbersome. I would just like the whole high level domain blocked.

Of course if I did get that ability, I would block all of western europe and a good deal of africa too. I’m sure it wouldn’t take long for the spammers to realize it and to start sending from more widely accepted high level domains, but it would be good for a while at least.

Is there a ligitimate reason for not blocking high level domains? Or, do some spam filters do it and I’m just behind the times?