Currently only the Oneworld RTW permits tickets to be issued in the US / Canada and converted to the approriate US or Canadian exchange from whatever currency it is based on. AA rates desk knows about this trend and that many people are taking advantage of lower currencies elsewhere.

But one must remember to originate from that country.

However, OneWorld members might restrict that rule soon so don't be surprised when you actually have to purchase and pay for the ticket in the country where you'll be originating from.