Hi,
Based on my understanding, there are only one OU that containing all the users. But you want to deploy different map drives to users in individual countries, right?
If i misunderstand you, feel free to let me know.
Since the map drive policy have the Item-Level targeting setting:
You can target the objects with groups or sites, ect.
In this way, we can deploy different map drive GPOs to different users even there are in the same OU.
Best Regards,