This is what common sense is telling me right now:
If you joined U2.com, then you are entitled to certain member benefits. One of these benefits is the RIGHT to take part in a presale. Now, it all cost us an EQUAL amount of money to join this club (forget the Prop deal for a moment). So, why would you believe that you would have the RIGHT to take part in TWO presales (1st AND 3rd legs NA) while Europe and the Rest of World will only get ONE presale?
If you use the code now, then you have used that part of your membership benefits up. If you don't use it now, then you are entitled to use the code (or some new code) at a later date. Our membership entitles us to access a presale ANYWHERE in the world. Once we use it, we cannot expect under any circumstance to be granted a SECOND presale IF WE HAVE USED OUR FIRST CODE.
What you would basically be saying is that the UK, Austrailia, Europe and Japan pay $40 and get one crack, while NA gets two cracks for the very same price of $40.