These are very good questions, and here's how I look at it:
Shelties were originally bred to herd sheep in a very specific environment. You can go as far as to say that they were bred to herd a specific type of sheep (small, primitive) for a specific kind of owner (generally poor, crofter) in a specific environment (harsh, cold, unforgiving).
Very, very few Shelties being produced today are going to be expected to do that job in that environment. This goes for so many breeds: how many Rhodesian Ridgebacks are going to be hunting lions on the Veldt? How many Norwegian Elkhounds are going to be baying moose just below the Arctic Circle? I don't think that it's necessarily a bad thing to recognize that our dogs are no longer expected to fulfill their traditional purposes.
So where does that leave me, the show-breeder? I think about what the modern Sheltie is expected to do: be healthy, stay sound, be a loving family companion. Yes, there are people who herd with their Shelties (and even use them in their daily chores on the farm), but their number is dwarfed by the number of people who do agility or obedience with their Shelties. The number looks even smaller against the number of people who just want a sweet, smart pet Sheltie.
We live in a very different world from that inhabited by the crofters of 19th century Shetland. Many breeders just don't have the opportunity to see if their dogs could herd (and how does a breeder from Florida determine if their dogs could cope with a North Sea winter?). Herding instinct isn't something that we place a high priority on, because our personal and national economies no longer rely on sheep and the dogs that herd them. There are niche breeders who breed Shelties with herding as a specific goal, but for the rest of us - why select specifically for an instinct that is no longer useful, and that the average Sheltie will have little opportunity to fulfill?
We DO evaluate how well a dog is put together, how balanced it is, how moderate. We evaluate temperament. We evaluate genetic health. And yes, we evaluate the "look", because we want to produce dogs that look like Shelties and are pleasing to the eye. I realize that this may not be a popular viewpoint, but I'm being honest. I don't think that those of us who don't have access to sheep should quit breeding Shelties, because Shelties aren't just sheep-herders anymore: they're wonderful pets, they're amazing agility dogs, they're brilliant obedience dogs, and they're lovely show dogs.
We could mourn for the loss of the traditional use of the Sheltie, but I don't think that our modern, suburban dogs suffer much for it. We do need to continue to strive for dogs who can do their jobs: the job is a little different now, but it still requires intelligence, soundness, and a good temperament.
I don't think that the US dogs in general have too much bone. Coarseness and clunky skulls are out there, and this is an extreme that must be avoided as much as its opposite (snipyness, fineness, fragility). Moderation is the key: a sturdy yet refined Sheltie remains the ideal.
I too think I know what you mean, but could you give a little explanion! Like I said I am still learning, boy is their lots to learn
When is the best time to evaluate puppies for proper underjaw? Puppies faces just look so different.
Yes, the head is judged the same regardless of the amount of bone.