In France, le cowboy (pronounced le coBOY) is a mythical figure. French people are often surprised to learn that real cowboys still exist. Lucky Luke, who "shoots faster than his shadow," is a French-Belgian co-BOY. To us anglophones his name sounds like lükilük.
In the British Isles, cowboy is a term of oppobrium. Most often heard in the phrase "cowboy builders," it is used to mean an incompetent swaggerer, often a cheat. No wonder they didn't like President George W. Bush and his cowboy hat!
Right now I'm in Utah, a place where young cowboys still grow up learning to bull-ride and herd and brand. It's a way of life, and not the worst.
Be careful about dressing like this in cowboy country if you're not the real thing. Pretty much everyone out here wears cowboy boots (I think of this as the American national costume), and cowboy hats look good and are practical when riding. But go any further, and you might hear someone say behind your back, "All hat and no cattle!"