If a singer's songs transcend musical genres, can you classify them as either country or rock?

This question seems a little tricky because the answer is too obvious to be accepted without further discussion. However, I will try to explain in detail the validity of my answer.

If we say that a song transcends musical Genres, it is because the song has gone beyond the limitations of rhythm; such a song is too great to be framed into one specific musical category. Because that is what genres are, musical categories used to define music.

Having mentioned the former, one can no longer enclose such a song into one single genre, sometimes it could be considered a "fusion" if two well-defined musical genres are overtly present in the song.

But all in all, the answer to this question would be no, you can no define any longer a transcended song into either or one musical genre, at most you could call it a fusion.