Taking the emphasis on privacy, the most obvious source to look at is F-Droid. So checking my [Call Blocker](https://android.izzysoft.de/applists/category/named/office_contacts_various#group_97) app list with that in mind (simply watch out for F-Droid icons next to the app names), **[NoPhoneSpam][1]** sounds like a good candidate – and meets your requirements (as I understand them):

* **can block calls:** sure :)
* **can block by country code:** Yes (quote: "Use special syntax to block countries or providers or parts of numbers")
* **respects your privacy:** Yes. Minimal permissions (read phone state, calls) – only those really needed. No network permissions.

Just in case, it's also [available at Google Play][2] – though I definitely recommend using F-Droid wherever possible (for privacy reasons).

Note, however, that this app hasn't been updated for about a year – which mustn't mean much, of course, as long as it works :)


[1]: https://f-droid.org/repository/browse/?fdid=at.bitfire.nophonespam "NoPhoneSpam at F-Droid"
[2]: https://play.google.com/store/apps/details?id=at.bitfire.nophonespam "NoPhoneSpam at Google Play"