They don’t show the fee as a separate item on a bill. It is built into the exchange rate they give you. If you have ever had to correct a charge immediately, you can tell. If there is no fee, there is almost no difference between the charges. If there is a fee of 2.5% say, the reversal will be about 5% less than the original charge.
I can’t believe that AMEX goes through a conversion to US$ and then to CAD$. I have never had that with Visa ans Mastercard.