Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
I am an immigration expert and DIFFERENT CONTRIBUTOR, not an author and informational specialist as your previous expert.
What additional questions did you have for us about the visa requirements for Brazil (they have indeed been lifted as you were told) and Argentina also has joined the visa waiver program as well?
You can see from the US State Department, no visa is required for Argentina: https://travel.state.gov/content/passports/en/country/argentina.html
Brazil typically requires a visa, but for the summer because of the Olympics they have suspended that visa requirement, see also US State Department: https://travel.state.gov/content/passports/en/country/brazil.html
Here is what the Brazilian Consulate says:
TEMPORARY UNILATERAL VISA WAIVER FOR CERTAIN NATIONALITIES DURING THE 2016 RIO OLYMPICS
American, Australian, Canadian and Japanese nationals going to Brazil exclusively for tourism activities, entering Brazil between June 1st and September 18th, 2016, will be eligible for a 90 day, non-extendable, unilateral visa waiver counted from the first entry within that period. It will not be necessary to have a ticket for an official game to benefit from this waiver.