Italian and American leathers are both codominant and are compatible. The difference is the Italian leathers are more smooth and uniform, the american leathers can be variable. You get some that are definately leathers, others that are questionable, and normal scaled. The italian leathers are either smooth, or normal scaled, no in-between. The structure of the two lines are different. Italian leathers are shorter/stockier, american leathers are longer/leaner.
When crossing the two lines(leather to leather), you will get a combo of the two lines(silkbacks), american leathers,italian leathers, and normal scaled. It is hard to distinguish between the american and italian leathers, that's why I don't reccoment crossing the two.
Josh