That is hilarious. I haven't seen much of Argentina's TV programming so I had NO IDEA that they portray the Mexicans the way the Mexicans portray them! You have described the soft J much better than I did. I am going to have to find an online TV station down there. I would love to hear the canto accent. Is it used in a particular region? How can I find it? Why do I imagine that is how Don Segundo Sombra must have spoken?
I believe the “canto” is from Cordoba. (It is many years since I was in BA). I have seen it described as “lilting”.
I have no idea how you could hear it, short of going there I guess!