THE United Nations has had a generally successful first half-century. Will the next 50 years see it becoming what we now need: a more representative, more responsive, United Peoples organization? We have seen small glimmers of this already. In 1991, the UN insisted on resettling Iraq's Kurds in their home villages, over the strong opposition of Saddam Hussein's genocidally anti-Kurd regime. And this year, the UN succeeded (almost) in establishing a ''safe space'' in Huairou, China, where people from 3,000 nongovernmental organizations (NGOs) could interact, expressing ideas that frequently were critical of official China. In times past, and certainly until well after the UN was founded in 1945, relations among states were enough to define nearly all of world politics. You could daub a map with different colors - pink for the British Empire, say, yellow for the French, and green for the Dutch - and anyone could assess the kinds of trade relations, the likelihood of war. But now, the empires are gone, and the powers of governments are everywhere eroding. In the years ahead, it will be relations among a broad mix of states, NGOs, global business, and intergovernmental organizations clustered around today's UN that will define the world. Groups like Amnesty International, Worldwatch, Greenpeace, and Doctors Without Borders - plus Mobil, Mitsu-bishi, CNN, and various cultural associations - will be writing the script for world history at least as much as most of the governments that now monopolize voting in the UN. Will this be a world that most Americans feel happy with? It would be comforting to say yes - to point, say, to the disproportionate preponderance of North American women in Huairou, and to assume that American ''enlightenment'' will help to transform the world. Comforting, but quite likely wrong. First, much of the tough work of building global NGOs like those mentioned above has been done not by Americans, but by others not so prone to operating on ''our-way-is-best'' approaches. Second, the facts of human interdependency have not been firmly established within American popular culture. Too many Americans - like too many Chinese - still wrap themselves in the illusion of self-sufficiency that being part of a great continental power can provide. Do you consider the warnings of ''militia'' members about the dangers of ''one-world government'' to be hopelessly paranoid and far-fetched? Well, paranoid they may be. But the militia supporters have at least as much influence on the mind-set of our representatives as the worthies of various national UN associations. So, worldwide and particularly here in the United States, much needs to be done. We need to press our government to give real, continued support to the United Nations and its institutions. It is outrageous for the US to be the ''deadbeat dad'' of UN member states. And we need to continue pressing for administrative reform of the world body and its institutions. But the complexity of the years ahead requires more than this. We need to brainstorm on how to get the interests of the world's peoples, and not just its states, represented in the world body. The way that NGOs now have observer status with the UN is just a start. But NGOs (like multinational corporations) have the drawback of never having been elected to represent anybody. Conceiving of, then building, a system that represents us all will take enormous creativity. Here in the US, though, the main battle for those of us who see the world as interdependent will still be to combat provincialism and isolationism in our own communities. A vast continental power - whether here or in Asia - that turns its back on the rest of the world would truly be a disaster for humanity.