What are the departure and destination airports of your example flight? I assume it is Hartsfield since Foothills is your first VOR. If thats the case, you can simply go to FlightAware's
IFR Routes resource page and plug in the US departure and international destination and reference the route. The NAT is in there as NATx, x being the track designator. If it is a European departure coming into the US, I would suggest routing it through the TOPPS intersection or one of the ones listed below. If you look at the link that SteveC posted, all of those fixes start with X and then have 4 letters which correspond to a couple of different fixes that are right on the border of domestic airspace;
XTAFF=TAFFY, XTUSK=TUSKY, XALLE=ALLEX, etc.