I have the exact same situation and mentioned it earlier in this thread. I literally never entered my number as Canadian, but that is what it shows. I am able to change it to USA, but as soon as I log out and log back in its back to showing as Canada. Very annoying.

Was thinking about calling Gold line to see if they can permanently fix it, but somehow I have a feeling how that will turn out.

Like you, I suspect it will work fine given the country code is the same, but it's just annoying that BA can't get the most basic IT things correct. They email you telling you to ensure your information is up to date and correct, but they literally cannot support properly updating the information when it's incorrect...

Regards