First, WikiAnswers is an English-language website, and the United States is the most populous English-speaking country in the world. As a result, there are likely more users on WikiAnswers who are American than from other countries. This means that there is a greater likelihood that questions will be asked about American topics, and that answers will be written from an American perspective.
Second, the United States is a prominent country with a global influence in many areas, such as politics, culture, and economics. This means that American topics are often of interest to people from other countries, who may seek out information and opinions from American users on WikiAnswers.
Third, the structure of WikiAnswers itself may encourage an American bias. For example, the "Most Popular Questions" section on the homepage often features questions about American topics. This may give users the impression that American topics are more popular and relevant, and thus lead them to ask more questions about these topics.
Finally, it is important to note that WikiAnswers is not a professional research tool, and the answers provided on the site are not always accurate or reliable. This means that it is important to use critical thinking skills when evaluating information found on WikiAnswers, and to seek out additional sources before making decisions or taking action based on the information provided.