Like Mikaela I'm Swedish. I live in Sweden and my VISA card is Swedish. I have however given a US billing and delivery address. It's a genuine address (my friend's home) and I have had Nook covers delivered there.
I have however not ever been able to buy anything but free Nook-books.
I can still do that (got the Rizzoli/Isles short story minutes ago). As far as non-free books I haven't made any attempts yet. Might try one of the $0,25 or something ones just to see...
Edit: Update: Nope, did not work. "Invalid credit card" or something like that. Previoulse when I have tried (way back in May) the message I got was that it was because I wasn't in USA, so something has definitely changed.
Edit 2: I realized I really wanted the $0,25 book (Bobblehead Dad), and (as usual) it was the same price at Sony Store where I have no problem using my VISA card, wherever I am physically located. So now I went and spent money and made my already too long TBR list even longer. It's supposed to be a quick read though...