Yes that's true, in Europe Amex is Rarely accepted by the shop, because of the fees,
The small retailers only takes Visa/MC and Cash
Another option for you, will be to buy a Visa/MC debit card at a mall in Europe and pay for it with your Amex, add somes funds to the debit card with your Amex, and use the Debit Card for your purchases where amex is not accepted