On Sept 14, 2019, there were some new electronic payment requirements for Europe.
It's called the: second Payment Services Directive (PSD2).
It looks like the transactions that must comply with the new requirement, are transactions where the seller's bank account is in Europe, and the buyers bank account is in Europe. According to the information, it seems like the seller will be exempt if their bank account isn't in Europe. So, if your bank account is in the U.S. then you shouldn't have a problem, even if the buyer is paying by credit card in Europe.
The new stripe system first requires a request to stripe to create a PaymentIntent object on the server.
It looks like there is some sample code on GitHub.
https://github.com/stripe-samples/checkout-one-time-payments
I guess that I'm not going to worry about this at the moment, since I'm not in Europe, and most people pay with PayPal.