Why do most countries in South America speak Spanish?
Most of South America consisted of colonies of Spain, or had
Spanish settlements, after the Spanish explorations and conquests
that began in 1492.
Central and South America are referred to as "Latin America"
because of the Romance languages introduced there (Spanish,
Portuguese, and French. In most cases, Catholicism also accompanied
these European conquests.
Brazil was settled by the Portuguese under the Treaty of
Tordesillas (1494), and the three Guianas were colonies of England,
France, and the Netherlands.