But why do we need federal government to do that? The UN could do it, a big NGO could do it, why the federal government? And even when the federal government does it, it's not designed for it.
Because the Federal Government is beholden to the people who own the resources, namely us. I don't get to elect the people at the UN, and NGOs don't answer to me. Even if I did get to elect people at the UN, my interests as an American are poorly represented by a large world government. The resources here belong to me as a citizen of this nation, so I want representation in how they're managed. The Federal Government isn't some random thing that was dropped on our heads. It exists because we're a sovereign nation with a need for some kind of central and united governance. It was concocted in order to address real problems that people living in large societies have, just like every other national government on the planet.