[tsukikage]

Because, as an English speaker, most video games you play are of American origin.

[turkthrower123]

As a Turk, I Believe that all games I play are of American or Japanese origin.

[krapp]

There are European game studios as well.

[stuxnet79]

But European game studios have to cater to the American market or they risk going out of business. The simple answer to OPs question is: Americans are always the good guys in gaming because the American market is a large one for gaming and a lot of what's trendy and tasteful in gaming has to have an American bias for this very reason.