From what I understand, there is a hardware and a software data base. Essentally that means that if you use a UK GPS with americas software data base then you don't get to see useful bits like lakes and shorelines. I'm no expert but a guy did think that his UK Garmin I think it was would work ok in the USA with a software database update of the americas and it wasn't very satisfactory. If you change your location to a specific one, somebody living closer might contact you to let you borrow their americas GPS