I know you can't operate a UK spec RNS510 in the States as there are issues, even after updating the maps. Whether it's a firmware issue of not I'm not sure, but I would be inclined to buy one designed and built for this market. I've seen that Jap spec one on Ebay loads of times (I presume he's listing it as a "Rare" one?), and no one else has bought it. That ought to tell you something.