I posted above about my experience, but I did forget that I had a return (to the US ticket) but it is beyond the 90 days. I tried showing that also, and it did not really help.
Some other options either mentioned here or other places are: You can by the Buquebus tickets (ferry to Uruguay) (the ones that are fully refundable or valid for a year) which most people will at least wind up using at least once anyway in a year. or you can buy a fully refundable airline ticket to Montevideo so you do not have to shell out like $3000 for one back to the States, or Europe.
I think it is as Elhombre says: the airlines policy not the country. Problem is it is a moving target.
