This document analyzes how cultural background affects the use of social networking sites (SNS) between Korea and North America. It discusses theoretical frameworks of individualism vs. collectivism and face culture/self-presentation theory. It then analyzes the distinctive features and users' behaviors on three major SNS - Cyworld, Facebook, and Twitter - and applies the cultural theories to understand the differences. While the theories provide some explanations for cultural variations in SNS use, the document notes limitations in broadly applying the frameworks across all sites and questions if they fully capture today's interconnected digital world.