My nook has a US IP while ordering the apps, at least
http://www.ipaddresslocation.org/ indicates that. Apart from the IP address there seems to be another network related characteristic which tells the B&N server that I'm not physically in the US at the moment although my IP address indicates that. Unfortunately, it's not possible so far to order apps from the B&N website and download them later. This seems to be only possible for books and mags (where it actually works from outside the US).