If you do sign up for Canada, you can leave your address there unless you are redeeming awards (since you can sign up for e-statements). Your Cdn office can forward the award to you anyway.

One suggestion to get elite status automatically: change your UA FFP address of record to a Canadian address, and then send a statement with this to AAdvantage. There is a status match offer (courtesy of CX apparently) for status. Look up "Canada Elite Offer" in the Air Canada/Canadian forum for details. You sould be comped to AA PLT.

I am not sure of the other oneworld partner FFPs but AAdvantage does give you the elite bonus for eligible oneworld partner airline flights. You also do have to fly 4 AA flights to requalify.

Another advantage to using a Canadian address is reduced requalification levels: 18k (instead of 25k) for GLD and 35k (instead of 50k) for PLT.