But where is our reason for believing it cannot remain his postwar plan? He was going to fly before the Borg came. And not for shits and giggles, because he personally hated the idea of doing the flight - he had some outside reason for doing it (or at least for agreeing to being goaded by Lily Sloan into doing it).
Riker says that all major cities have been destroyed, but from the rest of Star Trek it is clear that minor cities like Los Angeles, San Francisco, New York, Boston and New Orleans have not. The infrastructure context of Zep Cochrane is those minor cities and the continent hosting them. Sure, the great space fleets of China, India, Mexico and Brazil may be gone with the cities, but we have no particular reason to think that the spacecraft of the US, France, Russia or other bit players would be all lost or incapable of being relaunched on short notice.
I'll be honest: From what we see in FC, I really have no idea why Cochrane was still making his flight.
It's post-WWIII. Cochrane, Lily, and a few other Road Warrior rejects are hanging around Montana because that's where the silo is. Cochrane doesn't seem to have an official staff or overseers from any government or nation, nor does he seem to have any funding, either from the US or some other nation (and if he did have funding from, say, China or Russia, one would think that they'd have the means of providing him with a newer and better launch vehicle than an antiquated Titan missile.) When he actually makes the flight, no one seems to be monitoring it. The design of the Phoenix implies that after the flight, the crew module returns to Earth while leaving the main body plus warp engines floating in orbit without any apparent means of retrieving it. The whole endeavor screams of nothing more than a Virgin Galactic-style thrill ride conceived by one old drunk guy in his garage.
While Cochrane made it clear his original reasoning for building the Phoenix, surely he doesn't expect that to come to pass now. The way he makes the statement implies that that idea (getting rich and retiring to an island full of naked babes) isn't going to be happening. At least that's my interpretation. Plus, who's going to pay him? And what is this unknown party actually going to get for their money? The Phoenix's engines? If that were the case, then why didn't Cochrane just sell the Phoenix to them instead of flying it himself? The plans for building the engines? If they just need the plans, why does Cochrane need to launch the Phoenix at all?
Again, it seems like Cochrane is just making the flight to make the flight, for no real reason (especially when, as was pointed out earlier, he doesn't even
like to fly?) So why is he making this flight at all? It seems that the only reason it's happening...is so that the Vulcans will see it.
Earth wasn't so bad off as is commonly believed. Not long after Cochran makes warp drive a reality, just a year or so later the first warp colony ships leave Earth. Cochran speaks at a college just a few years later in Enterprise.
I'm pretty sure the reason why Earth bounced back so fast after FC was because of the Vulcans' help, not because the rest of the planet was in better shape than what we saw.
Spock: " The mid 1990s was the era of your last so-called World War."
McCoy: "The Eugenics Wars."
Spock: "Of course."
Translation
Spock confused the Eugenics War with WWIII,
McCoy gleefully correct him,
Spock conceded the point.
Actually, I'm pretty sure the intent was this:
Spock refers to the last World War (obviously WWIII, because if it was meant to be WWIX, they would have made that clear.)
McCoy agrees with Spock, but states the exact name of WWIII.
Spock agrees that WWIII was called the Eugenics Wars.