Think of the satellites DIRECTV, or any other place uses as a flashlight and the earth as a basketball. You can only get a signal where the light shines. In this case the light is shined on the USA. Argentina is on the other side of the world, is you split it at the equator. It is thus in the dark for that flashlight. So a DIRECTV (USA) box in southern South America will just read "searching for signal" forever. (Actually you would not even get that far, as the electric plugs and voltage are different, so the box will not even plug into the wall without adaptors).
DIRECTV Latin America is a totally different set of satellites, but is, obviously mostly in Spanish, although it has a few English channels.
Your best bet is some kind of internet service, or, if you have access AFRTS.