I don't think Protonmail is significantly safer than Gmail, when defending against US govt
Disclaimer
Quick Note
Assumes threat model of govt-level actors
Main
Proton servers for calendar and email are hosted in servers in multiple countries across the EU. Proton responds to Swiss courts. They have responded to subpoenas before, just like Google has.
I'm sure you can make an argument for why Proton is still marginally better than Google:
Higher probability of actually requiring a subpoena before sharing data, instead of just handing over all the data by default for bulk scanning. There is no proof for this, you just have to trust reputation here.
Higher probability of actually publicly updating their "number of legal orders", as opposed to just complying in secret. I don't see how this count helps much anyway, some legal orders are way more important than others, they are basically still complying in secret.
Does not block Tor connections
In theory, you can construct some edge case scenario where US courts would grant a subpoena but various EU courts would not. (I don't know of any real world case like this, but also, I haven't search that thoroughly.)
Allows anonymous users paying via cryptocurrency - I like this feature
If you are actively being targeted by US govt, don't expect Proton to protect your data. Use PGP / Tor / TAILS.
You can still use protonmail to transmit PGP-encrypted messages, just like you can use any random dark web forum to transmit PGP-encrypted messages, but assume that both of these will hand over all data and metadata they have on you.
Subscribe
Enter email or phone number to subscribe. You will receive atmost one update per month