So poor people driven out from their homes by a natural disaster, and by the failure of their country to respond adequately to that disaster, or to act responsibly to guard against it, should be deorived of the right to have a say in the future of that city in the aftermath because they realistically reciognise that it is not likely to be possible for them ever to go home to live?

Well, it's not quite "only in America", because there probably are some other places where that kind of thinking can be found. I wouldn't want to live in them though. (And in fact I don't believe that most Americans would share that way of thinking.)

But I'm still puzzled by all this. In my country an electoral roll is drawn up which entitles you to vote in a particular locality and it gets revised on an annual basis, to take into account changes of address. (And it's possible to get your name added to that electoral roll in the meantime, if for some reason you aren't on it.) But no matter where you have gone to live in the meantime, even if it's in another country, you are entitled in principle to use that vote in that locality for local or national or supranational elections. Isn't there an equivalent system in the USA?