Apparently Mexico's fans were too loud. Plus, they threw paper.
Frankly, I've always found it a weird custom that some stadiums play the U.S. national anthem at international friendlies where the U.S. isn't involved. Why bother? That equals three anthems when everyone just wants to get the match going. I'm not surprised that fans don't really acknowledge it under those circumstances. Think about it - at the Olympics, do they play the host's national anthem before every medal ceremony just because that's where it takes place? Of course not. Yet this writer is upset about that - and also apparently upset that game announcements were made in Spanish. During an Argentina/Mexico match.
Seriously, that's pretty ridiculous and petty. I read the headline and expected that fans had trashed the place, somehow negating the millions made off the match (and what is implied by the discount pricing subheader? That these fans are cheap? The Arg/Mexico match wasn't a cheap ticket). Depressing.