Actually it is not only the Collie that is affected that way. Most of the working breeds no longer work and are relegated to being rug warmers. We started in the Caucasian Ovcharka in 1998 and since then I have watched the temperament, and color change drastically - structure has also changed but to a lesser degree.  For instance when we got our first 3 dogs from Hungary they all had white mask and very sharp temperament. They were very difficult to handle and keep but they protected us and our property in Italy and then in Virginia. In those short 17 years you can hardly find a white mask CO anymore as the Russian Bear type were so heavily promoted and bred. The rise in popularity of the black mask was soon in favor in the show circuit and thus - that is what we have today. The dogs are much softer in temperament these days because the are now judged hands-on if you take them to a show or someone will call Animal Control if you dog barks at them. There may be a few breeders who still breeds the rustic or aboriginal dogs and I am actually hoping to find one. 

On the Working Collies - I did not realize they were so rare in the USA. I find that strange because they are such good herders and guards. I suspect they are a well kept secret out in the pasture lands of the Midwest and south.  I have a hunch that there may be a few in the Great State of Texas so will do some more research.  Stay tuned.