True, but if US non-residents were not taxed by the US, the whole issue goes away. In case I wasn't clear, even if "double taxation" doesn't actually result in

True, but if US non-residents were not taxed by the US, the whole issue goes away. In case I wasn't clear, even if "double taxation" doesn't actually result in double taxation or an additional tax obligation -- i.e. (owed_US - owed_foreign) > 0 -- then it's still an unnecessary headache for the citizen. In the US, thanks to extremely complicated rules and lack of centralized information collection -- many people use an accountant to file their taxes, which is much less common in other parts of the world. In my native Norway, for example, the tax authorities already have everything most people need to file, and indeed if you don't file at all they will simply calculate your taxes for you. (Unlike the US, they will mail a bill if you owe anything.) Living outside the US then potentially means having to use an American accountant to figure things out, unless something like TurboTax can do the job. (Last I checked, apps like TurboTax didn't do complex use cases like FBAR.)