thanks for your quick replies. They helped me find the solution.
The problem is that the Google search add-on that is installed in firefox re-directs the search to the local provider. Which is why I was coming up with Google Vietnam, because I live here.
To solve this I just hit the 'get more search engines...' link in the 'manage search engines...' window. Then I used the Mozilla Add-on Site
to search for google.com. Luckily enough there was an add-on specifically for me. The 'always google.com in English' add-on.
Thanks for your help guys.