They are?? I don't realy know much about America save it's location anyway, but I know loads about great Britain, my own country, and also France, Germany, Spain and Denmark.
Yes they are....
While denim trousers originated in europe and ...um, India, I believe... the association with blue jeans and america dates back to the wild west era. popularized in the 50's by actors like James Dean, they are one of the most common types of clothing today. I don't know how old you are, but I remember times before the Berlin wall fell, when blue jeans were worth hundreds of dollars to people on the eastern side.
Both the Spainish and the Chinese refer to jeans as "cowboy pants".
But yes... Blue jeans+Gasoline+applepie=Americana