the rep told me that if I chose to have the merchant charge in USD
(i.e., DCC) there would be no foreign transaction fee.
I'm not sure that is true. I think maybe he meant there would be no currency exchange fee. Over the years, I have asked many people at banks here what is the cost of foreign transactions with their bank, and I have received a lot of "inaccurate" answers.
I have not analyzed the foreign card processing network in a few years, but this was the way it was a then.
Use of cards in Europe are handled by the an informal collection of business collectively called "The Network". They are separate businesses handling ATM and Point of Sale transactions; they're attached to the card (Visa, M/C, ?) you are using. They all do the same thing. They handle the transfer of money from your bank to the ATM owners or retailers in Europe, and they convert the currency in the process.
Years ago, the Interchange fee, the fee they charge your bank for the service, was just called a "currency exchange" fee. Wells Fargo had their own foreign currency operation, so they said, "we'll just pay you in Pounds, Mark, Franc, etc, and then, since you're not exchanging currency, we won't owe you anything. Well, the Network operators weren't going to transfer the money for free, so they broke it up into a "Cross-border Transaction Fee", where they pay the European entity and bill your bank, and a "currency exchange fee". Each fee is about ½%, ±1/10%, for a total of 1%.
My credit union just passes the 1% fee to me. Some big banks, Bank of America, Chase, USBank, I think, pass the 1% fee they pay on to you and add another 2% for themselves (a 200% profit!). Wells Fargo, on my last trip, charged me $5 for an ATM withdrawal up to $500 in euro, which was just over 1%. A few banks, like Schwab or, I think Citibank (or is it Capital One), eat the 1% fee as a service to their customer (but since they're discounting the payment to the merchant by several %, they're not losing money).
So Citibank doesn't mind if you pay the conversion fee for them (DCC) and they only have to eat the ~½% Cross-border Transaction Fee.
On my last trip, Deutche Reisebank tricked me into DCC. I forget what they charged me for currency conversion, but it was more than 1% (vs. ½% from the Network). My credit union only passed on to me the ~½% Cross-border Transaction Fee, since there was no charge for currency exchange.
So is DCC a scam. Well, it is not a scam if you are told that it's optional and will cost you more that way, but otherwise, if it is snuck in or if you are not aware or you were tricked into believing you had to accept it, then it is a scam.