And do you really need a bank account per credit/debit card? I'd assume you have "external" credit/debit cards, where the only connection to the account is that it is charged monthly.
- You never know when you'll have a fraud alert and a disabled card. When you're travelling overseas, even if you call ahead to notify the card company, you're a lot more likely to get a fraud alert. You know how you can get stuck on hold with your card company, lost in touch-tone hell? Well imagine that on cell phone roaming charges with a dying battery on a noisy street corner.
- You never know what will be accepted. Some machines only take chip and PIN (which is the norm in Europe and Asia, they think signing a receipt is weird), sometimes a clerk doesn't know how to do chip and sign or swipe and sign (which is universal here in the US).
- Most of all, you're in a country where you dont speak the language, the ATMs look different, you might not be able to read the signs or even have a conversation with a cab driver.
When your card gets rejected, you want to have a backup. So, two credit cards (from two different providers) and two debit cards (from two different providers).
That said I have looked into cards with no foreign transaction fees for future international travel. They do exist, but one more issue is making sure they support "chip and pin" for European countries.
Using cards internationally can be hit or miss.