Google seems to be blocking certain searches

I have some insight into what the most common search terms are today for the NSFW Former Naval Person blog. What I see gives the impression that Google in the United States is blocking certain search terms. People are finding the prohibited content using search engines, such as Altavista, Yahoo Image Search, and Google and Google Image Search from other than the United States. Even Google from Canada can find the content, but people can't from the United States, using Google.