The casual approach to kilt wearing is not a uniquely American phenomenon/fashion. Short socks and walking boots or 'sports' shoes are not uncommon on this side of the pond as are T-shirts and leather jackets (think Monarch of the Glen).

The only uniquely American things I've seen are the US military/police style shirts and US military/police accessories - Civil War belt buckles, police work belts etc. All of which are hardly nontraditional.

Given the globalization of fashion I doubt if a uniquely American look could really get off the ground. An idea will get the same reception across the world. Either accepted or rejected.

I suppose you could design a jacket with 'western' features with a cut away front or one inspired by military academy dress uniforms or even a bolero type that would not appeal to the non-American taste but would it appeal to the American taste?

Hands up who would buy a kilt jacket with western features?