This sounds like it's an issue related with your bank trying to scrounge more money off you. I have a European debit card and I get charged the equivalent in EUR, nothing more.

You'll have to ask your bank since they're the ones screwing you. I've been using my US Wells Fargo account in Europe, and my British Lloyds TSB account in Europe and the US, and I've never gotten screwed anywhere near that bad. Maybe 1-5% premium I had to pay in some cases.

But in any case, you should look into getting a USD account. I have a USD and EUR account from Lloyds TSB International and it is a good way to guarantee I never get screwed even a little bit when I'm traveling and doing a lot of small transactions.