The rest of the world should be allowed to get a vote in the election for USA president

I work in London - a great world city with a powerful elected mayor who has power over evertyhing from the public transport I use every day to the Olympics we just enjoyed. But every four years, when it is time to elect the mayor, I don't get a vote. Because I don't happen to live in London.

I know that's how it works, and that I choose to be a commuter (because I can then afford to live in a house rather than a small flat) but there is still a democratic deficit if I get no say over the appointment of a politician who has so much influence over my life.

But it doesn't stop there. In this ever-globalising world there are lots of other powerful people, elected and not elected who have a great influence over my life. And it's not just me. Angela Merkel, the German chancellor, probably has more impact on ordinary Greek people's lives than the Greek Government.

And, the newfound economic power of China notwithstanding, the most powerful man in the world is still the President of the United States, POTUS himself. He has influence over the lives of everyone on the planet, but one the quarter of a million US citizens get to vote in the presidential election. Is that really fair?

I know it would be unprecendented to open up elections to citizens of any country at all, but some countries (like the UK) allow some resident aliens to vote, which seems only fair.

I'm sure there will be plenty of objections. The President has more impact on Americans than he will have on the rest of the world so it would be unfair if US citizens could be outvoted. But perhaps we could have some system where US votes count double or even ten times non-US votes.

Also the President is paid for US taxpayers. We have heard of "no taxation without representation". What about "no representation without taxation"? But then non-taxpayers who are US citizens are still allowed to vote. Maybe overseas voters should have to pay for the privilege? But then that would be unfair to the world's poor.

In this globally connected world we live in, if we want to make progress on so many things that affect all of our lives, like global warming, peace in the Middle East, or nuclear disarmament, the President of the United States (and the leaders of other countries like China and Russia) probably make more difference than our own leaders, so you can understand why we want to have some say in who they are.

But ultimately it is impossible to have a completely fair and representative system. Even a democratic world government could not guarantee that.