I think they changed the "resident fares" a couple of years ago because I haven't see any remark or any information about it (warning) when booking on Ar vs US website in a very long time, the only difference for now is the AR version you can see and buy Super Promo and Promo fares (if you are lucky to find one), while any other country will only show you Base/Plus/Flex and above.

For Carry on, 8kg still a limit, but they wont check that, they may take a look if your carry on looks too big. For Domestic, 15kg on checked luggage if your tickets include it, otherwise you need to pay for the first 15kg, and an extra if you are over 15kg but less than 23kg (limit for domestic).