You have to file federal taxes. Maybe state taxes. You don't necessarily have to pay depending upon how much (in USD) you make. Things also depend upon per-country tax treaties. The shitty part, at least for me, is that I can't use the ISA and similar programs here in Japan for retirement because the US considers them all passive foreign investments (PFICs) which require copious paperwork and punitive taxes wiping out any tax-advantaged retirement savings. Also can't just invest non-taxed income in many things in the US either.
Voting being at the state level also just fucks all kinds of other things up with taxes and the like.
A friend told me about rust around 8 years ago and this was very much my first experience (at least with &str and lifetimes and borrow errors).