If something doesn't help people overall, then it really has no value. That seems pretty odvious. Should we sacrifice the world for an individual? of course not.
The real question in this is HOW we can help the most amount of people the most, but we can only get to that after we decide to actually think about a way to get that done.
Remember we still need things like limits to mob democracy and a law system to better everyone, this does not mean a political free for all. That would lead to an eventual dictatorship, which is not good for the greater good.
But you are right that other people envy American wealth, but we need to ask ourselves if that envy is validated or not.
Many people from all over the world really do wish that they had the wealth that Americans have, and it isn't that they all want to take it from us, but that they just want an opportunity to compete and then excell.
If you look at the jobs in many developing nations they are much, much more strenuous and have lower pay then the worst mininum wage job in the US. Those people are not useless demanders, they just have no way to better their lives.
There is way too many people on the Earth, that is why we should focus our welfare on getting people out of poverty, and not just simply giving food to people where we will just slow their death a few years.
That is the best choice for the most amount of people, individual selfishness has nothing to do with it.