@tabish - this happens more often than I’d like to admit. :)
I think you’re on the right track using “Country” as the proxy, but you may want to verify that they are “Consented” (Subscribed) and not just have the Profile added into Klaviyo.
It’s a bit tricky, since “Consent” can be gathered by Klaviyo directly (if you use Klaviyo Signup Forms, or properly integrated apps that pass on Consent) or by the ecommerce platform itself. If however, you collect emails in other ways (uploaded a List? have other tools that push emails into Klaviyo?) - it’s not obvious if they are “Consented” or not unless you made sure to mark them as so or you had Double Opt-In enabled.
To be super safe, I’d export only people in those regions that also have “Consented” in Klaviyo, and export Consented folks from the Email Platform to have a clean Subscriber List as you migrate them to their respective proper Klaviyo Accounts. And of course, you may want to export the Suppressions List just to pass those on as well.
For everyone else that you’re not sure, a well retargeted Klaviyo Popup to have them “re-optin” might help - even though that may not be the best user experience. But with the right messaging (and offer?) it might close the loop on those ambiguous “Consents” to be on the safe side.
If you want to go the extra distance, once you have migrated, you may want to isolate those new imported folks with a “quality” Campaign to those folks and monitor its performance + bounce + spam complaints so they’re not blended into the averages.