This is done because psychologists believe that people see themselves as iconic in there own mind, which is without a whole lot of detail. So seeing a cartoon character in a simple iconic form lets us look farther into that character and sometimes take a greater interest. This is also known as a masking effect, which became the style for Anime and Magna. So seeing chariturs in iconic form helps some of us relate to the characters situation. Anime also shares the bright colors with its American counterpart.
Bright colors attract the eye and adds another attractive feature to cartooning.
The differences between American animation and anime are quite obvious. Eyes in anime are generally vary large with a thick black line going over the top of the pupil. Eyes can vary, and become stylized as with any type of art. American animation generally has no set usage of eye style but tend to give chariturs large oval shaped eyes, though usage of anime style seems non-existent. Hair on characters also is extremely different.