TIL: US citizens living and working in Australia have our superannuation (mandatory retirement savings, like a 401(k)) taxed by the IRS as ordinary income. Including investment earnings. Even if you have moved to Australia permanently. That's actually fucked.
(I am not trying to argue that the US tax system is good or fair. I'm just trying to work out my own tax situation now I'll seemingly be doing US tax returns for the rest of my life)