Brittish Collies are smaller with weight between 22 to 32 kgs and height between 55 and 60 cm. American Collies height is between 60 to 66 cms and weight between 27 to 34 kgs.
The official colors of Rough Collies are blue merle, tricolour or the famous Sable and White. The official breed standard states, that all white or predominately white Collies are Highly undesirable. That is another problem for American Collie lovers, because there is a lot of them in white colors.
The first Collie was imported to USA in 1897 by Allen Apgar and because his Collies started winning dog shows, other people wanted them as well. Today, Collies are very popular in USA and it is no wonder, they are excellent dogs. The American Collie head is narrower and slimer and their eyes are smaller. Those differences are not big, but definitely noticable.