Further, these tax treaties differ from country to country and don't always offer the same protections. Here, read the 42 page US/France tax treaty (https://www.irs.gov/pub/irs-trty/france.pdf) and try to figure out how you'd be impacted if you were living in France.
We expats don't just have to hire accountants to do our taxes, we often have to hire international tax lawyers, EVEN IF WE DON'T EARN ENOUGH TO PAY US TAXES!
Studies have repeatedly shown that the majority of expats are abroad to find a job, to teach, to volunteer, or for love. We're taxi drivers, waiters, English teachers, farmers, computer programmers, and so on. We're normal people who are being massively screwed by rhetoric in the US.