If you want to do a US Residency do not go to med school in another country (with the extremely slim exception of Canada, Britain, or Ireland). Your credits are not likely to be recognized as equivalent to US schools. You will be treated as foreign trained, and odds are before you can even do a residency you will be forced to repeat at least one year of med school.
In Canada for instance, Residencies are given to Canadians first, and only in the rare situation that there actually is a residency position available after the match is done, does a foreigner get a position. This includes Americans -- so if a position is available after the match, you take it -- even if it's a residency in geriatric oncology and you wanted to study orthopedics.
Believe me, my sister in law is Dutch and finished med school in Holland then immigrated to Canada. She ended up working 6 years for Terry Fox foundation, putting her name in for a residency every year, until one year, luck of the draw, she got a residency in Vancouver (hematopathology). It's like the bloody US Green Card lottery -- you put your name in every year hoping that your magic number will be drawn.
Foreign trained doctors who have already been practising for years (15 or more even) are regularly required to go all the way back to doing last year of med school + residency before they are allowed to practise in North America. Be very careful what institutes you choose to study at, you need to go to one that already has very strong ties with the USA if you want to try to get back there.
My sister is finishing a Maternal Fetal Medicine fellowship right now -- there's only 2 jobs in Canada at the moment for her, both in crappy cities (one of which is FULL of immigrant doctors because they are the ONLY people willing to work there). She really doesn't want to go to the crap town, so she looked into going to the States. She's already done her American boards etc -- what's the problem? Her fellowship isn't recognised in the States. They won't acknowledge her last 2 years of study. And that's between the States and Canada -- be prepared that your Argentine medical school degree will only get you credits for two years of med school, and then they'll want you to repeat the rest.
Have you looked at Guadalajara? They are supposed to have a very good med school with strong ties to the States. It may be better to consider that over Argentina. What you want to find is a school where you have the option of doing a semester or so in the USA. If you can't study a portion in the USA, you're going to find yourself having a hell of a time getting back there to practice.
If you study abroad, recognise that you are going to end up doing your residency abroad. At your age, I'm not sure if you are thinking of doing a specialty. GP is only 2 years residency, so I don't know if you'd be able to take a rotation in the USA to at least beef your experience up for trying to move back there. The one advantage to doing a longer specialty would be the possibility of doing rotations back in the USA. Unfortunately, most rotations go the other way round -- ie US medical residents doing a rotation in a 3rd world country to be able to practise procedures or in conditions that they just would never have a chance to see in the USA.
The place where more opportunities open up is if you do a fellowship after your residency. In canada a certain number of fellowship spots are specifically reserved for foreign-trained doctors. getting a fellowship as a foreign-trained doctor does come with the possibility of being able to stay.
So think of it this way -- Med school abroad, residency abroad, fellowship possibly in the USA. Career if lucky after fellowship, in USA. If not, abroad.
