Here's a question: who should be allowed to vote?
For example, should people in prison be allowed to vote? Should children be allowed to vote? Should an unemployed hobo be allowed to vote?
Well, I can't hear your answers, so here are mine:
A person in prison should be allowed to vote, because if there is a candidate (or law) who is trying to make the crime that the prisoner was imprisoned for legal, this would clearly be something that would be of interest to the prisoner. The same goes for any candidate or law that changes the parole rules, the level of evidence required to put someone in prison, the types of evidence that can be admitted to court, or the level or type of punishment that can be meted out. We might wave the prisoner's right to vote at such a time that we become certain that we have a perfect justice system that will be permanently in agreement with the voting public's opinion. But we are a while off from that.
Children should have a vote by proxy. Children's political interests are as real as anyone's, but their understanding of their political interests is low. Parents should vote for them. This should arguably give parents the right to vote once for themselves and once for each of their children. Of course, this only holds if we can trust the parent to act in a child's interest, which is demonstratively not always the case. Ideally, each child should have someone voting on their behalf. Someday we will work out some system that implements this in a realistic way. In the meantime, we should ignore this issue.
The unemployed should be allowed to vote for the same reasons that a prisoner should be allowed to vote. I hope that the reasoning here is self-evident.
The common theme here is that people who have a personal interest in the laws being made should have the right to vote on those laws. I am writing from within a representative democracy, so as far as I am concerned, every citizen has the right to vote in every election. If I lived in a direct democracy this would not always be the case -- I might not need to be part of a vote on a law regarding the legalization of marijuana, as I have no interest in the mater, either direct or indirect. I do have an interest in a law on social security, as I hope to retire one day, a law on military funding, as I both pay taxes and am at risk if we are invaded, and laws on immigration policy, as I enjoy neighbors who speak Spanish but dislike ones who speak French.
Of course, our laws on military funding and immigration policy are also of direct and pressing interest to the rest of the world. Iran would have loved to have voted on our military budget; Mexico would love to vote on our immigration policy. More importantly, many Mexican citizens would love to vote on our immigration policy. They have a very direct and personal interest in this matter. Some various foreigners have a life-and-death interest on some issues of American policy, which surely gives the the right to vote -- certainly more right than I have to vote based on a few percent change in my tax rate. Pretending that their needs are less important just because they are not American citizens is no different than refusing the vote to women or blacks or Catholics.
Amazingly, this is not generally considered to be self-evident. Our legal (and therefor our moral) universe is not held to contain all of Earth or all humans, but rather all of our countrymen. This is obviously purely arbitrary. There is no moral or legal benefit to being bombed in Cambodia vs. America... or perhaps more relevantly, being tariffed in China vs. America. The only difference, the difference between life and death or profit and bankruptcy, is which side of an imaginary line you are on. And you don't get to decide which side of the line you are on.
This is not an obvious boon to the universal human right to pursue life, liberty, and happiness.
Therefore, this is not in compliance with the United States Constitution. Nor for that matter, does it comply with common sense or human decency. And while there are barriers to getting a universal vote, it is reasonable to suspect that most of the world will help with the local polling stations. Those who wont allow their citizens to vote should obviously have a proxy assigned to predict what is in those citizens best interests, and vote accordingly.
Of course, there will be those who say that someone has to look out for the Americans, and the whole point of having a country is to have a political unit that will look after the people who belong to it. Obviously, there is some logic to this argument, but just as obviously, this argument only works if each political unit has approximately equal political power (or, if you like, equal power per citizen). It makes no sense to say that a wealthy nation has the same need to advance itself on the world stage as a small, starving nation.
The only moral thing to do, then, if we truly see the default human state as that of a being of moral worth and consider all humans to have approximately equal rights, is not to prevent outsiders from voting, but to grant voting rights based on needs. Someone facing starvation should get a sizable wad of votes every time an issue of food tariffs, bio-fuels, or genetically modified crops comes up. If you live under a violent dictator, you should have a significant number of votes to spend on America's immigration policy. And this is not really something that should be in question -- unless you have a very odd idea of human rights.
If that's not enough for you, consider the possibility of making this sort of voting system a new world standard -- which is to say, that Americans would be able to vote on China's economic policy, or Mexico's drug war. And if they don't allow this, they are clearly abusing basic human rights, and should receive appropriate consequences for being so evil.