I’ve literally never heard the name of Garth Brooks before, honestly. In my life, I’ve heard about I think literally two country artists (from googling him, I understand he’s a country artist), Loretta Lynn and Dolly Parton. And I suspect most people my age (30) in Spain haven’t heard of them either, even ones quite into music.
Country as a genre just never features anywhere in Spain, and in my experience in most of Europe 
It’s not a “big” genre for us at all. I also don’t know who are the best selling artists in the history of, say, Chinese or Japanese pop, although I imagine they’ve also sold many millions of records.