> Is that an EU-issued specific phenomenon?

Not as far as I'm aware. It certainly happens with GBP-issued and having briefly looked at some of the agreements, it happens with various Asian issued cards too.

To clarify:

      - If the transaction is in your "home" currency, you get charged in that.
      - If the transaction is in USD, you get charged in that.
      - Everything else is subject to double-conversion

Example wording below from the GBP card (the last phrase of the last paragraph is the important one). I see they no longer charge double-fees, but you will still loose out on the double currency conversion because there will be a double-spread on there:

     If we receive a transaction or refund for processing in a foreign currency, we'll convert it into Pounds Sterling on the date it's processed (which may be different to the date of the transaction or refund).

     This means that the exchange rate used may differ from the rate that applied on the date of your transaction or refund. Exchange rate fluctuations can be significant.

     If the transaction or refund is in U.S. Dollars, we'll convert it directly into Pounds Sterling. In all other cases, we'll convert it into U.S. Dollars first and then into Pounds Sterling but we'll only charge one non-sterling transaction fee.