The American Shih Tzu is typically larger than their European counterparts, with an average height of 10-11 inches and a weight of 14-26 pounds. On the other hand, the European Shih Tzu is smaller, with an average height of 7-11 inches and a weight of 10-26 pounds.
The American Shih Tzu has a thicker coat that can be straight or slightly wavy, while European Shih Tzu has a softer and more delicate coat that is often wavy or curly.
American Shih Tzu has a square-shaped head, forward-facing legs, and wide-set eyes, while European Shih Tzu has a more rounded head, shorter snout, and more closely set eyes.
The European Shih Tzu tends to be more affectionate and loyal to their owners. On the other hand, the American Shih Tzu is more independent and can be left alone for longer periods.
Regarding trainability, the American Shih Tzu is generally easier to train than the European Shih Tzu. They are more intelligent and can learn new commands quickly.