It gets a little confusing, because you'd think all Kit Kats would be the same, but if you ever look at the U.S. Kit Kat packaging, you'll notice it'll say it's produced by Hershey's, while any Kit Kats outside of the U.S. have Nestlé printed on it.
You're probably wondering how the hell this happened, but when Nestlé bought out Kit Kat from Rowntree (Kit Kat's creator) in 1988, the Hershey Company already had a previous contract to produce Kit Kats in the U.S.
Nestlé couldn't pry those rights away from Hershey's, so to this day, 'Merica is the only country in the world that has non-Nestlé produced Kit Kat bars.
Because of this, all those cool flavors in Japan, Australia, Canada, and everywhere else in the world, come from the minds of Nestlé, while the U.S. has to be content with the minimal flavor efforts of white chocolate, strawberry, and the ever-daring "Dark" chocolate bars that Hershey's goes with.
Kit Kat might eventually break out and start giving U.S. customers cool flavors, but until then, we'll have to envy the rest of the world as we bite into our basic milk chocolate bars.