I did the same thing but except with a EU Game Time card, I ended up just giving the code to a lucky EU for free since NA doesn't even have a game time card of its own.

I wish you luck with your exchange but I am sure that the majority of people who made a similar mistake as you did have already done their exchanges. The only thing that I can possibly recommend is selling the EU Collectors Edition for a little cheaper than you bought it, take the deficit that you have, and then repurchase the NA CE version.

That is all I can really recommend to you if you want this resolved quickly.