How are the cultures in south america like the culture sin mexico? how are they different?

The similarity lies in the common Latin American culture - they both Speak Spanish, listen to same music, share religion and many core ideas. In fact, many people describe it as the same culture.
The difference could be described as a "regional variation" - Mexico is slightly different due to its closeness to the United States and for example the Mariachi Music is typical of Mexico but not of the other countries. Also, Mexican Spanish incorporates many Nahua words, which the other countries don't.