So not only is it double taxation but it is taxation without representation, something that's generally considered bad...
As an American abroad, this makes little sense to me.
Rather than spread our votes out across the country by forcing us to vote where we last held residency, why not allow Americans abroad to elect their own representatives?
I have more in common with other Americans abroad than I do with the average voter in the state where I last lived nearly 20 years ago. We wouldn't expect a former New Yorker, now Texan to continue voting in New York's elections. But if someone moves from New York to, say, Mexico City, that's exactly what happens.
It would be nice if people simply voted and paid taxes where they live, and moving to another country was easy, removing the need to hold on to previous nationalities.