In the U.S, usually a birthday party is organized by the person who is going to have birthday.
Nyankichi : Hello~ Next weekend is my birthday, and I'm gonna have the party. please come come. ( Nowdays, this information will be post on Facebook, by the way..)
I haven't been familiar with this custom. I still feel something strange about organizing my birthday by myself. So didn't have birthday party by myself.
Nyankichi : I think this custom is very practical! Like it!