MONTERREY/GUADALAJARA, Mexico, June ⁠18 (Reuters) - First came the factories, then came the food, and then the pop tunes took over. South Korean fervor in Mexico has been years in the making, ⁠growing into a mass movement that has seen President Claudia Sheinbaum share a balcony with K-pop royalty BTS, and visiting World Cup fans greeted with ‌the chant: "Korean, my brother, you're now Mexican."