What the Baha'i Faith envisions is a federalized system of government like the United States, with only questions of international concern decided with the centralized government. Before I say any more let me quote from Shoghi Effendi:
The unity of the human race, as envisaged by Bahá’u’lláh, implies the establishment of a world commonwealth in which all nations, races, creeds and classes are closely and permanently united, and in which the autonomy of its state members and the personal freedom and initiative of the individuals that compose them are definitely and completely safeguarded. This commonwealth must, as far as we can visualize it, consist of a world legislature, whose members will, as the trustees of the whole of mankind, ultimately control the entire resources of all the component nations, and will enact such laws as shall be required to regulate the life, satisfy the needs and adjust the relationships of all races and peoples. A world executive, backed by an international Force, will carry out the decisions arrived at, and apply the laws enacted by, this world legislature, and will safeguard the organic unity of the whole commonwealth. A world tribunal will adjudicate and deliver its compulsory and final verdict in all and any disputes that may arise between the various elements constituting this universal system. A mechanism of world inter-communication will be devised, embracing the whole planet, freed from national hindrances and restrictions, and functioning with marvellous swiftness and perfect regularity. A world metropolis will act as the nerve center of a world civilization, the focus towards which the unifying forces of life will converge and from which its energizing influences will radiate. A world language will either be invented or chosen from among the existing languages and will be taught in the schools of all the federated nations as an auxiliary to their mother tongue. A world script, a world literature, a uniform and universal system of currency, of weights and measures, will simplify and facilitate intercourse and understanding among the nations and races of mankind. In such a world society, science and religion, the two most potent forces in human life, will be reconciled, will coöperate, and will harmoniously develop. The press will, under such a system, while giving full scope to the expression of the diversified views and convictions of mankind, cease to be mischievously manipulated by vested interests, whether private or public, and will be liberated from the influence of contending governments and peoples. The economic resources of the world will be organized, its sources of raw materials will be tapped and fully utilized, its markets will be coördinated and developed, and the distribution of its products will be equitably regulated.
National rivalries, hatreds, and intrigues will cease, and racial animosity and prejudice will be replaced by racial amity, understanding and coöperation. The causes of religious strife will be permanently removed, economic barriers and restrictions will be completely abolished, and the inordinate distinction between classes will be obliterated. Destitution on the one hand, and gross accumulation of ownership on the other, will disappear. The enormous energy dissipated and wasted on war, whether economic or political, will be consecrated to such ends as will extend the range of human inventions and technical development, to the increase of the productivity of mankind, to the extermination of disease, to the extension of scientific research, to the raising of the standard of physical health, to the sharpening and refinement of the human brain, to the exploitation of the unused and unsuspected resources of the planet, to the prolongation of human life, and to the furtherance of any other agency that can stimulate the intellectual, the moral, and spiritual life of the entire human race.
A world federal system, ruling the whole earth and exercising unchallengeable authority over its unimaginably vast resources, blending and embodying the ideals of both the East and the West, liberated from the curse of war and its miseries, and bent on the exploitation of all the available sources of energy on the surface of the planet, a system in which Force is made the servant of Justice, whose life is sustained by its universal recognition of one God and by its allegiance to one common Revelation— such is the goal towards which humanity, impelled by the unifying forces of life, is moving.
Shoghi Effendi, “The World Order of Bahá’u’lláh” , 7.109