I have found that the big banks in the United States partner with banks in other countries to use ATM's without a fee. In Canada for example, Bank of America partners with Scotia. You also want to check with your credit card company and your bank to see how exchange rates are caculated and, for credit cards, to see if there are additional fees. In Canada, my U.S. Visa credit card charged a 3% fee for every transaction. (I didn't know this until I returned home and saw the extra charge on my bill for every transaction). Had I known that, I probably would have relied a lot more on getting cash from Scotia ATM's, rather than using my credit card so frequently.
In addition, some countries require the use of the pin number for credit cards, something that is not required in the U.S.