Out of curiosity I just contacted @fastmail to see if they hosted my email in Australia. Turns out they don't, its all US-based.
I knew they had offices there but this is something else, calling them an Australian business isn't really true. Honestly I'm pretty disappointed and not sure what to do next.
I get that places still host in the US but I was working to de-Google myself and ultimately reduce my reliance on it, and this just kinda sucks.