US has double tax avoidance agreement with many countries. So if you are a US citizen living in country X, you end up paying taxes to US & X, both. But a reason

US has double tax avoidance agreement with many countries. So if you are a US citizen living in country X, you end up paying taxes to US & X, both. But a reasonable chunk of the "double" tax can be recovered when you file your returns. It's not that bad if you consult a tax expert (good international tax experts are rare, quite a few are misinformed). P.S. US isn't the only country that taxes you on your worldwide income.