We call them "sprinkles" in this here fine land of Indiana. I have heard jimmies before on a cartoon that had an argument about what to call them, but I have never heard of anyone call them jimmies. If jimmies are actually a variant of sprinkles that are distinct, then that is interesting. But I know of no such variants here.
Regardless, I have only had them a handful of times in my entire life. Not a fan of them for their taste and color.