There is a distinction between prepaid credit cards and gift cards. I'm not sure why, but prepaid credit cards typically require a SSN and gift cards don't.

They end up working just about the same though. You can buy them both at a retail store for cash, and use them just like a credit card anywhere Visa/Amex/Discover/whatever is accepted.

To activate the credit cards? I'm pretty sure you don't - you just need to plug in any old address and phone number online which aren't verified (at least with the gift card ones), kind of like a burner cell phone.

You might need to get European cards, though, and I'm not sure how they work over there or how easy they are to get.