Brazil is the largest country in South America, fifth largest in the world and has had a big role in comic books. One of the major features of Brazil is the amazon Rain Forest and the river which gives this forest its life. Often times the area is attributed in comics without mentioning the country it is from (though smaller areas of the Amazon Rain Forest and River Basin exist in small regions in other countries.) Most notable is the Beatriz DaCosta who was born there and had a large role as a Brazilian spy and a business owner. She also represented Brazil in the Global Guardians.
The Atom also had many adventure in Brazil when he discovered the city Morlaidn. It was here that me met Laewthwen with whom he fell in love and this is the reason he kept going back.
Also, the Parliament of Trees (Swamp Thing), in The New 52, is located in Mato Grosso, a big estate in the middle of the large South American country.
Same in the Titansverse: Mirage and Allegra Garcia were born there.
Comic Book Locations
Nova Roma - A Roman city located deep in the Amazon. (Marvel Universe)
Morlaidn - A city of six inch yellow warriors aliens who came here to live and set up a primitive civilization. (DC Comics).