I don't use the "Edit" button for name/address info (& make sure the "Show this window again when address is incomplete or unclear" checkbox in that "Edit ..." window, is not ticked)
This particular section seems to have a default format which struggles with longer/international address layouts. Instead, I always type the info directly into the "Bill to" section on the customer record.
Alternatively, if you do use the "Edit ..." info window (or add Shipping addresses), type the address - as you want it displayed - all into the "Address" box & ignore the other fields (City, State etc)
Sorry Kevin ... I get where you're coming from now. I had thought you'd meant on the invoice itself.
As a workaround, would it be any good to create a Custom Field for the Country? This can be added in their Customer record which you can then add to your invoice template "Screen" to autofill every time you create an invoice for them, but not display on the customer's printed/hard copy. Then filter/group your report by this?