Post from this expat blog suggest there may be a crackdown going on in Argentina against people who are essentially living there by repeatedly coming and going on tourist visas.
http://baexpats.org/topic/31498-i-wa...try-at-ezeiza/
Maybe the OP got caught up in this, he/she refers to visiting Argentina many times. This wouldn't explain why the USA would have told Argentina not to let him in, if that indeed happened.