In terms of Australia being late to the party vis-a-vis joining a united earth government, and I apologise that I don't know if there's an analogous incident somewhere in US history, but here in Australia when federation of the six dispariate colonies under a single federal government was first being proposed in the 1800s, the entire affair rested on each of the colonies coming to the table, and if only one of them dropped out then the deal was off... and a couple of them (West Australia and Queensland) did in fact procrastinate and pull their support at various times, to the point where it looked like federalism was dead at some stages of the process (and it was only ultimately achieved in 1901 after significant concessions were made to the state of New South Wales to get them on board).
So, there are historical prescedents for this kind of thing.
Obviously Australia *did* ultimately join the united earth in Star Trek's timeline, but I could understand if (for example) there were some doubts about it happening during the event itself. 
So, there are historical prescedents for this kind of thing.

