If this is all on one ticket with the domestic leg on AR, I wouldn't be terribly worried about it. In the worst case, if you land in EZE too late to make your flight, AR can put you on another flight - they have a few. In the worst worst case, you might have to make it to AEP on your own, but that's not a huge problem if you have a few hours between flights.

I definitely would NOT do this if your flight to USH is on a separate ticket, particularly if it's with one of the low-cost carriers. It's not unheard of for airlines in Argentina to suddenly move their flight departure times up by a few hours. I personally wouldn't risk it.