I don't think I've ever seen them in the U.S., but then I might not have noticed because I've stopped eating lollipops for so many years now (at one point I began thinking they're disgusting, I don't even know why but I certainly still feel that they're disgusting).
You could find Chupa Chups lollipops everywhere in Thailand when I lived there though, like in the candy aisle and right by the cash register. I loved them back then, especially when you could get Spice Girls stickers at one point.