It either comes with a supply expecting 100V 60Hz or a universal one that is 100-240v, 50/60Hz. I'm not sure if stores are swapping it out or if newer ones come with the universal one.
Universal is definitely ok.
If it's the 100v adapter, then it should be okay, plenty of people use Japanese stuff directly on US mains with no issue. 120 is only 20% more than 100v so standard sort of tolerance anyway.