I ask because the cowboy tradition originally came from Spain and later it was transferred to New Spain as the terrain is similar. As I understand it natives started out as ranch hands, then the Irish settlers and so on.
At what point did this transition into a wholeheartedly American identity?
Was it possibly with Hollywood Westerns?
I would argue that Theodore Roosevelt helped contributed to the image. Though he was born in a rich family in New York City, he later lived in the Dakotas on a ranch and took on a "cowboy" lifestyle. He had a huge persona to back it up too. A big man of the outdoors, a war hero,etc.
Though, I would say that western films were a huge factor. They were extremely popular in Europe in their heyday, just look at spaghetti westerns. Films leave a large imprint on people.