Australia
Australia holds an interesting role in the century following World War III. Spared any direct strikes from that conflict, and suffering only the slightest environmental concerns from the literal fallout, Australia became uncharacteristically conservative and isolated. Taking charge of a large part of the ISA's infrastructure, it did not administer it for the world's benefit, as the United States did, but asserted control for its own national purposes. Many of the orbiting (and transiting) vessels that re-flagged with the Australians did so for understandable reasons: the home planet appeared to be devastated and without support from below, survival of those in space was in peril. Later on, as the US exerted additional control over the network, some space assets would transfer allegiance, but most did not, avoiding any appearance of being something to be fought over.
Australia used the defensive spacecraft to assure that no remaining faction could possibly harm the sub-continent (for what ever reason they might have) and eventually expanded that mandate to cover Australian interests, including economic endeavors on other continents and their ships at sea. Australia had a number of scientific vessels under its control, too, and it bargained with the US to exchange those for as many of the resource miners the Americans were willing to trade. This was done in direct competition with the new breakaway nation of Texas, which was also more interested in mining assets than in the pursuit of knowledge.
Australia maintained its alliance-free isolation for quite a long period of time, including with the arrival of the Vulcans in 2163. In its world view, the Vulcans were just as suspect as the rest of humanity and that Australia only had a self-supporting capability to loose. However, it agreed to abide by the Sparon-DeSoto Treaty and allowed its space forces to be (somewhat) controlled by unified (and non-partisan) command (though its vessels commanders were sworn to never turn against any Australian asset). When the United Earth Stellar Navy was formed in 2069, the Australians agreed to give up their space forces completely, in return for access to a number of aging mining ships. It would, however, remain outside the New United Nations.
After several generations of Australian independence, the nation (and a few of its Oceanic allies) refused to go in on the Traité d'Unification in 2130; the United Earth government, for its part, left them alone but was also adamant that it would not work to establish most favored status for them with the Vulcans, Tellarites, Denobulans and other assorted interstellar neighbors. As the Australian economy stagnated, and as fear of a post-scarcity backslide evaporated, they came around and signed the Traité, finally and truly uniting the planet.