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/
and with owners in the US, there's even more legal jeopardy potential. where the servers are located is less relevant than who owns them.
contrast that with Tuta, sure it's EU owned but you have to go through more layers to get to account details, and not as easily strong-armed.
though the French MS email saga from a while back makes it all muddier. French authorities will comply with requests made through the proper channels, a US judge said she didn't have to and demanded compliance - putting MS-France in non-compliance with the US court order, or non-compliance with French law.