Same thing I said to the other guy:
Irrelevant. Also, not absolutely true.
My post isn't about the US. I said this much in my note at the very top.
Don't divert the conversation towards irrelevant US-specific details.
Where your statement isn't true is in that there are myriad taxes and other proposals and laws people vote for that only affect someone locally. For example, the dopes in our area voted to tax ever square foot of property that blocks rain from making contact with raw dirt. Someone in Australia could vote for that measure. It would not affect them one bit.
There's so much that never even touches income taxes, which is what would affect people living abroad. And, in reality, there are foreign income tax credits and other rules that change the tax equation for anyone living outside of the US.
And then there's the political/ideological allegiance element I mentioned. A citizen from country A emigrates to country B and retains voting rights in country A. Knowing they are not coming back and wanting to benefit their new country, B, they vote for measures and politicians in country A that would benefit country B.
How is that a good idea?
Again, get away from US-centric thinking here. This is about the general idea of the relationship between countries A and B, when a citizen who can vote in A's elections permanently relocates to country B.