You mean, not the first point brought up by the GP, was which to say wrongly that it was an American company?
Correct me if I'm wrong, but if Fastmail moved servers outside the US, then it would be in a better position as a non-US company than if it was a US company with servers outside the US?
Despite what some might believe, where a company operates from is actually important, regardless of where the servers are hosted.
As in, the actual point, which is that your e-mails are liable to be searched by the NSA.