There are two separate card issues going on here - let me explain.
The bank/credit union/(possibly credit card)
cash withdrawal at an ATM. You need a 4-digit, non-alpha PIN (your financial institution will provide you with one that meets these parameters if you contact them). Your withdrawal limits will reflect the currency exchange (just because you can pull USD300 at home does not mean you can pull EUR300). Many overseas banks have relationships with European banks, which will reduce or eliminate the foreign-institution service charges. There are service charges by both your bank and the ATM bank, but it's still cheaper than the old travelers check fees. ATMs are frequently, but not universally, available in the small towns along the Camino. Comments elsewhere in this forum warn against making withdrawals during non-banking hours, in the event the ATM is hungry and eats your card - as it means you will have to remain in town until the bank reopens to recover it.
The
credit card format is an entirely different issue.
No US bank currently issues, or has plans to issue, the (chip + PIN) format credit cards commonly used in Europe. The US (mag strip + swipe) cards will work everywhere there are credit transactions attended by humans (hotels and restaurants that take credit cards). The problem arises where there are only automated kiosks (parking, road tolls, rail and bus stations). Unless there is a human at a nearby window, Americans have been out of luck. Fortunately, the Travelex (
http://www.travelex.com) people are now offering pre-paid cards in the European format at their airport currency booths here in the US. You can get these in GBP or EUR denominations, load up as much as you like, and top it off later on. I don't know the situation with Canadian bank cards, but I suspect they use the US card format.