It isn't that simple in practice unless your finances are trivial. Even under a tax treaty there are a several circumstances where you'll pay more total taxes t

It isn't that simple in practice unless your finances are trivial. Even under a tax treaty there are a several circumstances where you'll pay more total taxes than if you solely paid taxes in either country. Tax incidence is determined per income type, it is not based on your total tax return; you can pay more taxes locally than you would in the US and still owe a lot of taxes to the US. Similarly, differences in definitions, recognition, taxation across types of income can differ between countries such that you end up paying taxes that are not recognized by the US and therefore are not credited as taxes paid. It is pretty complicated. The US tax code places an indefensible burden on expats. Also, some States (looking at you California) can require you to pay income taxes even if you live overseas for the entire year.