Fabrics were becoming cheap and available in Europe with the creation of factories, and these items were quickly shipped to the American Colonies. The French and the English had led fashion trends for the world for centuries, but in 1775, Colonists started to give ideas to the Europeans. News of the North American West with its beavers, furs, and backwoodsmen affected European fashion.
(Portrait & Hat: Bicorne hats like Napoleon wore were made of American pelts; notably beaver like this one that was supposedly shot off his head while he was wearing it)