How about this?
Why don’t you propose a name for the Country-Improperly-Known-As-Macedonia?
Think of something catchy, easy to say, that the people who live there would like.
Or, you could just relax and stop worrying. Nobody is going to mistake slavic Macedonia for Greek Macedonia. Isn’t going to happen. People call themselves whatever they want to. People understand that New Mexico is a US state, and has nothing to do with Mexico. New England is a US region, and has no current ties to England. We call ourselves US of America, and we manage not to get confused with South America. Somehow it all just works out.
LOL