Weird. FastMail is many times faster than Proton ever was for me. FastMail is also headquartered in Australia, not the US. Fastmail also now has European servers.
https://www.fastmail.com/blog/fastmail-offers-eu-data-region...
EDIT: Re-reading your comment, maybe you meant the fact that the servers were exclusively in the US (until very recently).
Data regions like these offer no protection, it’s just a feel-good marketing term with no legal basis. Source: I work in this business with multinationals with a similar footprint and we have paid actual lawyers to look at it.
The only thing that unfortunately matters here is that Fastmail has a US incorporation.
Fastmail even writes as such:
> If what you need is a guarantee that your data remains only in the EU, we don’t have that, and we’d rather tell you directly than let you assume otherwise.