Unlike most characters in America, Hello Kitty's design is manipulated constantly. 600 items are replaced each season to keep Hello Kitty collectable and the prices low.Hello Kitty Pop Culture Series
Here is a link to 88 different variations of Hello Kitty associated with pop culture, many of which are designed off of American characters or icons.
In the U.S., Hello Kitty stands for "girl power" and whimsy. She is marketed more towards younger girls who still find appeal in "cute" things.
Hello Kitty is mainly seen on clothing and items in America. One third of her products are produced through collabs and other companies.