You must file income tax in the US. If you are a full time resident in Argentina (there is a minimum number of days that you must live outside the US) you are exempt from tax in the the first $80,000 dollars you earn. The US embassy should be able to advise you.
Where are you claiming you are living? Are you coming in here on a work visa and working for an Argentine company? Or will you be working as an IC? That will have a good deal of effect on your tax status..
I am a US citizen living in Argentina and I do freelance work for US companies. Last year I went and saw the embassy tax adviser and they where actually quite helpful although they are only there a few days a year during tax time. You can get all of the information you need from here: U.S. Citizens and Resident Aliens Abroad. Don't bother calling the embassy, they will not tell you anything for fear of 'advising' you on tax matters. The first year that we moved here (moved in June, so it was a partial year), I payed taxes in the US as normal, claimed all monies I made as freelancer and payed tax on all of them. The second year I filed a form 2555 which gives you an exemption of around $80,000. I filed the 2555 with a 1040 which had a zero balance because of the exemption. The reason I was not exempt the first year was because you need to live here for 330 days or more to be considered your tax home. Quite simple really. I am no accountant, but this is working for me. PM me if you have questions.