This is a great question. In a broad topic such as drug trafficking what you need to do is narrowing things down. A strong thesis will be of central importance. In light of this, let me give you some suggestions.
First, you can talk about the economics of drug trafficking. You can explore the question of who stands to gain the most from an economic point of view.
Second, you might want to talk about the legalization of certain types of drugs. What are the pros and cons of legalization? You can pick a side and argue for it. This can also be directly related to the idea of trafficking. For example, if the government regulates drugs, then certain drugs will not be trafficked.
Third, you might want to explore how the government can reduce drug trafficking. If you go this route, then you can offer a few suggestions of how the United States government can work with South American countries to limit the drug trafficking.