To the average person, the difference between a German Shepherd bred in America versus one bred in Germany may not be readily apparent, but the differences are numerous in both physical appearance as well as temperament and working ability. If one were to visually compare the German lines with American lines, the most immediately noticeable difference would be in the angulation of the back and hind-quarters. American German Shepherds are typically bred to emphasize a long body with strong angulation in the back and hindquarters. Their build is often leaner with longer muzzles and a thinner head. On the other hand, German bloodlines often have a heavier build. Their heads are more square, and their backs are slightly sloped without excess angulation. Concerning temperament, the most important difference is in nerves. American bloodlines have a reputation for producing milder dogs with weaker nerves. German bloodlines, especially West German working lines and East German DDR working lines, are bred specifically to have strong nerves and a strong desire to work.
The key thing to consider is that American bloodlines are bred as show line dogs for aesthetic qualities over working ability. While long bodies and angulation may look nice, American show line dogs lack the balance, speed and agility required of protection dogs and guard dogs. This does not mean that working line dogs cannot be bred in America, but any capable working dog bred in America will be bred from import German working line dogs. German bloodlines have been bred exclusively for utility and working ability since the original development of the German Shepherd in the late 1800s. The Schutzhund trials were originally put in place to maintain to working ability of the German Shepherd breed. German working dogs who do not posses the required strength, agility and nerves simply aren’t permitted to breed. This ensures that only the best and brightest working line dogs are produced in Germany. Unfortunately, the same cannot be said for breeding standards in America.