the earth. it is comprised of many countries, each with its own military. yet the earth itself has no military of its own.
All fine and good, except that "The Earth" is not a political entity. There is no "Earth" representative body, no "Earth Senate", no "Supreme Chancellor of Earth". I do not rely on an "Earth government" to determine taxation rates.
I think the closest real-world analog to the Galactic Republic as presented in the PT is the League of Nations. It was an association of governments that was dedicated to disarmament, peaceful resolution of conflicts, had no military of its own, and relied on member states' militaries to enforce its decisions.
There are a couple of big differences, though: 1) Any state that wanted to could withdraw from the League, and no military action was considered to force them to stay in. 2) The League lasted not quite twenty years before being revealed as a grotesque failure with the onset of the second world war.
My issue with the Republic as presented is not that it never would have existed, but that it certainly would not have existed as it is presented in the PT for millenia.