Modern "liberalism" has abandoned American constitutional government and replaced it with democratic centralism, which, in fundamental theory, is identical with the democratic centralism of the Soviet Union, and of every other major nation existing today.
It was possible to enlarge the size of the old American federal union without diminishing freedom for the people. When you enlarge the land area and population controlled by democratic centralism you must necessarily diminish freedom for the people, because the problems of centralized government increase with the size of population and area which it controls.
Look at what has happened to America since our federal government was converted into a centralized absolutism. The central government in Washington arrogated to itself the unconstitutional power and responsibility of regulating the relationships between private employers and their employees, enacting laws which established "collective bargaining" as "national policy," and which, to that end, gave international unions a virtual monopoly over large segments of the labor market.
It follows that a minor labor dispute between two unions on the waterfront of New York is no longer a concern only of the people and police in that neighborhood. A handful of union members who have no grievance whatever against their employers but who are in a jurisdictional struggle with another union, can shut down the greatest railroad systems in the world, throw thousands out of work, and paralyze vital transportation for business firms and millions of citizens all over the nation.
Harry Bridges on the West Coast can order a political demonstration having nothing to do with "labor" matters, and paralyze the economy of half the nation.
Imagine what it will be like if we join a world government. Then a dock strike in London will cripple, not just the British Isles but the whole world.
Now, the central government in Washington sends troops into local communities to enforce, at bayonet point, the illegal edicts of a Washington judicial oligarchy concerning the operation of local schools. If we join world government, the edict and the troops will come (depending on what nations are in the international union, of course) from India and Japan and the Congo.
There was a time when Americans, learning of suffering and want in a distant land, could respond to their Christian promptings and native kindliness by making voluntary contributions for relief to their fellow human beings abroad. Our central government's foreign aid programs have already taken much of that freedom away from American citizens–taxing them so heavily for what government wants to give away, that private citizens can't spend their own money the way they would like to.