Q: iCloud Two-Step Verification Countries List?

Hi, I am from Bulgaria, EU and I don't see an option on iCloud.com to enable two-factor authentication. I go to iCloud.com / Manage My iCloud / Password & Security and I can't find the "Get Started" to enable it. I wonder if my country is supported and where is the list of the fully supported countries. I will be glad to see that Apple will release this worldwide. Facebook, Google, Twitter and tons other big companies do support it worldwide as I know, why don't Apple do it too, if this is the case?

Kind Regards