Can a single social media platform like Facebook have the potential to increase or decrease political polarization in the United States? This book will try to answer this question using a systematic literature review. 34 studies on the effect of Facebook use on political polarization in the United States were identified and analysed. Contrary to the widespread belief that the use of social networks such as Facebook increases political polarization in the United States, slightly more than half of all the studies analysed in this paper concluded that Facebook use does not affect or even decreases political polarization in the United States. Explanations and implications are discussed.