If you pay Proton Mail for a service, they may hand over the payment data in response to a court order: https://www.404media.co/proton-mail-helped-fbi-unmask-anonymous-stop-cop-city-protestor/
You can actually pay Posteo in cash by mail: send banknotes in an envelope with a code to Posteo.
@Tutanota as alternative does not offer direct cash payment, but you can buy Tuta gift cards cash same way via the reseller Proxystore.
@protonprivacy also accepts cash payments according to their support, by sending physical money via post. You get the details by contacting Proton support…
But if you pay with a Creditcard, you have an US provider an board
