Because the Spanish-speaking countries of South America were all once colonies of Spain.
Yes, in most of South America
There are many more than 2 countries in South America.
All countries in South and Central America speak Spanish with the exception of Brazil, Belize, Surinam, French Guyana, and the Falkland Islands.
Spanish is the official language throughout South America, except for four countries. For the official language of Brazil is Portuguese. English is the official language of The Co-operative Republic...