I have the same problem as you.
Here you can see very clearly where hanger/skirt steaks come from:
https://www.goodfoodstories.com/hanger-skirt-flank-flatiron-...If you look at the next link, our "entraña", Nº 17 in the illustration, should be the same.
http://www.asadoesargentino.com/la-entrana/But the "entraña" we know matches the aspect and description of "skirt steak" better. I would not be surprised if both pieces were sold as "entraña" in Argentina.
As for Mexican cuisine: this is how "skirt" is described:
"Skirt steak is the traditional cut for fajitas, and it’s a great way to acquaint yourself with this cut if you haven’t yet sampled its flavorful charms. It’s a loooong piece of meat, though—the usual pound and a half is a few feet long—so portion it out and freeze what you won’t be marinating for a quick stir-fry when you need it."