Currently in the Convert Countries UI for the new State & Country Picklists feature, only an exact match will cause an existing data point to not show up in the Convert Countries UI, the screen where you map your existing data down to the new standardize options in the picklists.
Right now, only exact matches will cause an existing data point to not show up in the list of Countries you need to map. It would be very helpful if it was possible to ignore case and just match on the strings. ARMENIA == Armenia == armenia == ArMeNiA etc. This would dramatically reduce the number of things that have to be mapped, and would speed up feature adoption.