I think the trick to this sort of mixing of cultural elements "working" is in the context - by which I mean geographical context. I think it helps if the wearer is actually in one of the geographical locations of the culture. For example, the outfits here pictured with kilts, cowboy boots, and cowboy hats, make sense to me if the wearer is at a Highland Games in Texas. Or perhaps worn by someone from Oklahoma attending a Highland Games in Perthshire. It's that blend of mixing the traditions of one's heritage with local traditions that makes sense.

But if I saw the same outfit being worn in New Hampshire, or in Boston, it wouldn't make as much sense to me. It would look like someone is just trying to come up with some strange outfit by throwing things together that don't really belong together.

It needs that local context to make sense.