That is an excellent question for which there is not easy answer.  Some of the dogs that enter North America are brought here specifically for their working abilities and are not usually see out in public.  The danger of the breed (dogs) changing and being ruined is when they have a "breed club" or other organization that tries to get them into the American Kennel Club which is a death knell for dog breeds. Breeders of AKC breeds do it for a variety of reason .. and one of them is for money.  When breeding for money becomes a driving force the breed is doomed to change from their original function.  It is laughable when I watch the Westminster Kennel Club show in New York and listen to the announcer proudly state the reason the dogs were created and what their functions are supposed to be.  I often wonder - when is the last time a dog from that line did its duty.

So you did ask a great question and I am sure my comment may have offended some - but for the most part - if a breed in North America gets popular and has breed clubs "promoting their preservation and protection" they are doomed.  Now, there are some exceptions where individual breeders do care and keep their dogs working even if they are part of a club.  Those I respect very much.