This is hardly accurate. Cultures regularly "throw away" and then later rediscover (re-popularize) pieces of their own historical culture / identity. It has nothing to do with it being preserved by another culture (such that if it weren't, it could have never existed again).
That's true, the rediscovery of American heritage clothing may have happened anyway, but I have to imagine the boom in American workwear/sportswear has been made dramatically easier for modern designers thanks to the Japanese otaku that have studiously collected, documented it (Free & Easy, Lightning Magazines) and continued to produce it (Buzz Ricksons, Real McCoy). Due to this, a route to revitalizing an American heritage brand is to simply hire a great Japanese designer. If no one had cared I do think it would have been a much more difficult process and I do think it would have been likely that some knowledge could have been lost.
