Participants from Latin America or the EU countries do not need a visa to visit Brazil. For participants from other nationalities, wikipedia provides a map with countries whose citizens do not need a visa, please check:
https://en.wikipedia.org/wiki/Visa_policy_of_Brazil

US citizens need a tourist visa to visit Brazil. Information about consulates in the US and visa application can be found in the following link:
http://washington.itamaraty.gov.br/en-us/