Hah.
No wait. Okay your forgetting about real soldiers to, or if theres still a military around, walking about saying their in charge, but don't really help much at all, then the ones that defect at least. And the biker, well he's likely USED that shotgun before despite what you think about Left4Dead. Zombies to him was just getting the 2 week party started. But the other two? I'd have to agree. Dumb luck brought them through the thing. Well dumb luck and bullets. And the other two who seem to be familiar with bullets.
What was my original point? Oh right. Your forgetting about people who have used firearms before, or have gotten survivalist training. Or really, your forgetting with god blessed dumb luck of the land, or whats left of the land, and the worlds JUST okay as long as no crack pot nation or some rather dumb world leader doesn't launch any nukes as a last measure. Course, I'm kinda betting on the crack pots first.
As for the army? I'd say they wouldn't have been defeated completely, or at least what we have in the U.S.A, so will have a army running around, or at least standing around. The only problem is that they won't be likely to help, and more likely to gun you down and strip you of any useful weapons and ammo. Sad but true. If I'm right, one thing the movie would be correct about is that being one of the last powers in the country that have tanks, 'copters, and maybe even jets still, won't be keen on protecting a country, that isn't THERE anymore. Whatever leaders of any military in the world, IF their still standing, will grab hold of whatever defendable compounds they can get their hands on, clean the area of anything useful, including man power if need be, and you know what I mean about that one, with their men under lock and key, and just forget about the outside world. At least, until things calm down. Maybe in a few decades, when you happen to be plowing a field to keep a small collective of people you found to come along with you, just to keep alive, you'll wipe sweat off your brow and look over the horizon. Bam. Round in the head, you don't know anything. The armies back, and their keen on rounding everyone up. Or at least the NEW crack pot of the NEW world is keen on rounding everybody up. You know what happens from there. Think PPA from Dies The Fire. Only likely with some zombies waltzing around still.
World in flames all right. World in rotting flames.