Hi,
How about using AcyMailing for this ?
It has a direct integration with HikaShop so that you can automatically add customers to lists and / or send them emails after their orders.
It doesn't support filters on the country as far as I'm aware. That's something you could request to AcyMailing if necessary.
Otherwise, if you want to use another tool like Mailchimp, you'll want to export the emails and import them to Mailchimp.
You could use a mass action with an action "export CSV file" on the "order" data type, with the user_email and the billing address coutry fields. That would give you a CSV file with the customers email address and country and you can then open it in Excel, and process the list there to split it based on the country. For example, with something like this:
www.ablebits.com/excel-split-table/index.php