Christian C. Karam is a Brazilian archaeology student who has written a paper with the controversial, if not provocative, title of Phoenicians in Brazil(a). In it he proposes that an encounter with an extraterrestrial body caused a global catastrophe, which caused a large part of the Andes to be uplifted, the Sahara to be dried out and Atlantis in the Atlantic to be submerged. He dates this event to around 9500 BC and believes that the Atlantean survivors fled to Africa.
Perhaps the first to suggest that the Phoenicians visited Brazil was Georgius Hornius in the 17th century. The matter was dealt with in greater detail(d) by the Austrian professor of history, Ludwig Schwennhagen, who flourished at the beginning of the 20th century. A Hungarian website(c) offers more on the development of this claim.
Karam names the Phoenicians as the thalassocratic successors to the Atlanteans. The main portion of his paper concerns the possibility or as he sees it, the probability, of Phoenician visits to and even colonisation of Brazil.
Ross T. Christensen (1918–1990) an American archaeologist supported the idea of Phoenicians in America. However, in my view, his early work as a Mormon missionary must bring into question his objectivity. Further evidence in support of Phoenicians in Brazil is presented elsewhere(b).
(d) https://www.academia.edu/7848641/Fen%C3%ADcios_no_Brasil_parte_1_Ludwig_Schwennhagen (Portuguese) (offline Feb. 2016)
Brazil has had few serious investigators propose it as the location of Atlantis. Although, in 1947 Harold T. Wilkins claimed[0363.97] that Quetzalcoatl was from Atlantean Brazil. Earlier in the 20th century, Col. P.H. Fawcett, the famous explorer, disappeared while searching in the Brazilian rain forest for a ‘lost city’ that he called ‘Z’. A 2009 book by David Grann about Fawcett’s searches in Brazil, entitled The Lost City of Z  was the basis for a film released in 2016. Sprague de Camp listed[0194.329] a George Lynch supporting a Brazilian Atlantis in 1925. In fact, Lynch was a fund-raiser for Fawcett.
However, although there is growing evidence of ancient roads, plazas and bridges in Brazil’s vast tropical forests, further data is needed before we can attempt to fit these structures into any specific culture or chronology.
An article(e) in the August 2017 of Antiquity offers evidence that humans lived in Brazil more than 20,000 years ago, which is many millennia before the Clovis people arrived in North America.
The possibility of Phoenician contact with Brazil has a number of supporters and a range of websites supports this controversial view(a). One such advocate, Ronald Barney, maintains that they concentrated their influence in the northeastern region of the country citing the work of Ludwig Schwennhagen and Apollinaire Frot(f). There would appear to be evidence for 3rd century AD Roman contact with Brazil(h).
May 2013 saw a flurry of media interest when a Japanese submersible found evidence in the form of granite suggesting of a previously unknown continental mass that sank about 900 miles off the coast of Rio de Janeiro. Members of the expedition have played down any attempt to link this discovery with Atlantis(b)(c).
This reminiscent of the reaction in 1931 when two islands were reported to have emerged from the sea off Brazil and within a short time, claims that they were a returning Atlantis were widely quoted(d).
Any suggestion that the land of Hy-Brasil in Irish mythology has any connection with Brazil or Atlantis is just wild speculation.
(g) See: Archive 3480