It's funny, because the Costco credit card used to be AmEx. IIRC Costco Canada only takes Mastercard, which is funny since the US Costco credit card is Visa, so you can't use the US Costco CC to pay in a Canadian Costco.
You actually can use the Costco US Visa at Canadian Costco, they’ve got a special exemption for it. (And vice-versa, you can use the Canadian Costco Mastercard at American Costco.)
