Two parties

Why do Americans believe that there can only be two political parties? I know Americans are not bright but most of them can still count to 10. So why do only two? Is it media brainwashing?

Those parties are the same anyway. Both are liberal and capitalistic. Both support torture (Guantanamo), starting wars, total espionage (NSA), mind control (CIA), etc etc. There is no difference whatsoever except perhaps a couple of decimal digits in some number in a health reform.

So why do Americans believe that they have a democracy when what they have is the choice between two names for one and the same thing?

Rooting for one of two sides is part of American culture. Elections have been this way since Thomas Jefferson. The Congressmen and Senators tend to have much more unique views, from extreme socialist to fascist. Generally people say the USA is a democracy because it is in practice. Nothing major happens without majority support. The majority supported both wars, otherwise it would have never happened. The same goes for Nazi Germany, btw.