If some countries and places of South America can be cold... why do we relate South America with the tropic?

South America is a pretty big place, while the Equator runs through the northern part, the southern tip is pretty close to Antarctica. In terms of latitude Uruguay is about 30 degrees south which is roughly equivalent to the Gulf coast of the United States which is about 30 degrees North latitude, and the southern parts of Argentina and Chile are equivalent to parts of Canada in terms of distance to the pole.