Is Wikipedia biased

In some areas, yes. In other areas, no. The wikipedia is free for anyone to edit - and, as a result some people may introduce biases or prejudices into the articles that they edit.

However, there is a series of checks and counterbalances which prevent this for the most part. Unfortunately, many of those who control those rigidly follow a politically correct construct that is biased itself.

Although, due to the wikipedia's large American user-base, the wikipedia does exhibit an incredibly large bias towards America, Americanisation, American views of other cultures/governments/etc., American English (as opposed to English, or English English as referred to in America), American Culture, etc.

For example, American celebrities or specialists may get entered into the wikipedia far more easily than celebrities and specialists of other nationalities - and a short time after the Swine Flu epidemic broke out, the wikipedia page for the 2009 outbreak listed almost every suspected case in America, whereas the Cases in Mexico, which numbered in it's hundreds (and later thousands) and is where the epidemic started, received nothing more than a a couple of lines.