I got the same email, and I don't have a credit card on file with them. I wonder what they're going to do?
Is this really the normal way to do this in the US? Does no billing info mean you’re immune? If they have your real name in Germany, they would just send it to collections and get their money if you really owe them something, even if they don’t have a way to charge it directly themselves.
Even if they sell the debt to collections, the collections service is probably only going to pay them fractions of pennies on the dollar, since "bill for random service someone signed up for the internet" is not likely to have a high recovery rate.