ahhh Viva La Mexico refers to a well known bull ring in Mexico City. We call it La Plaza Mexico, which is feminine. So, we say ‘La Mexico’, short for La Plaza Mexico. You’d only say el Mexico if it referred to a place (like a stadium called Mexico), but I don’t know of any… I have a masters and am Mexican.
https://www.spanishdict.com/answers/102487/would-you-say-viva-la-mexico-or-viva-el-mexico