ROTTWEILER BREED STANDARD
The two largest and most well known pedigree registries in the world are the American Kennel Club (AKC) and the Fédération Cynologique Internationale (FCI) also known as the World Canine Organisation (yes...that's spelled correctly). Each purebred pedigree registry (AKC, FCI and other) has a written standard which is a set of physical and temperament attributes to a unique breed. That 'standard' defines the ideal appearance (size and shape), gait (how the dog moves) and temperament of the perfect Rottweiler. In all recognized registries and countries, the physical attributes of the Rottweiler are consistent . There is no difference between American and German (or any other country) Rottweiler physical attributes although in most countries outside the US, Rottweiler tails are not docked but even the tail, has a defined standard. Read more about the AKC and FCI breed standard here:
AKC OFFICIAL STANDARD OF THE ROTTWEILER
The ideal Rottweiler is a medium large, robust and powerful dog, black with clearly defined rust markings. His compact and substantial build denotes great strength, agility and endurance. Dogs are characteristically more massive throughout with larger frame and heavier bone than bitches. Bitches are distinctly feminine, but without weakness of substance or structure.