Yes, I've done it.
I simply called to Amex customer service and explained what I wanted to do and why. After I was transfered around, I came to someone who could do it. They took all the usual applicaiton info plus the info on my CAN$ card. I cannot remember if they were able to tell me right away whether the card was approved or not, but it did seem pretty painless. They require a US address (you should be ready to convince them you have moved to the US).