Probably a bit hard to make, but you'd think in 15 years, someone would have got around to it. Or stole one from a museam and refurbished it.

Yeah, but that's a different thing. The metal-jacketed rounds, with smokeless poweder (that Pellegrino's character referred to) are probably beyond reproduction without electricity, but the guns they were using to shoot up the rebel hideout were probably of recent make. They were black powder muzzleloaders, which can only fire about once every 10 seconds, in the hands of an expert, their accurracy is none too great and their range & power is greatly inferior. Better than spears, which is why the militia uses them, but nowhere near modern military tech.

You're forgetting a couple of things. The 18th century did not happen on its own, it required lots of people with skills that had advanced a lot since the Stone Age. Granted, modern people retain a lot of the knowledge, but not much of the actual techniques of doing the things they know how to do. I know of several ways to start a fire without matches or a lighter, but I would not want to trust my survival on my ability to use a firebow or flint and steel. What's more, all the stuff they made do with the 18th century has been replaced by stuff that relies on electricity in some way, like steam engines giving way to diesel or muskets to automatic weapons. Natural seeds have been replaced by genetically engineered seeds, some of which have actually been made sterile, that is, they don't produce seeds of their own, forcing you to buy more seeds next year from the same company. Now when those crops are used, they're gone for good, and someone has to scramble to replace them with normal strains.

Without electricity, motor vehicles are all dead, except for maybe some old classic cars, and maybe them too. Those wierd magic necklace thingys suggest it's not just a lack of generated power, but something actively inhibiting the power, which means it's probably stopping sparkplugs and car batteries from doing whatever they do. All of that means there is no transportation over long distances. The country has become specialized, with food being grown in a few places using super-efficient techniques and shipped all over the world. There is no place to grow food in cities, and no means of rapidly getting it TO cities. There is no way to store perishables long term. There is no widespread distribution of pharmaceuticals. There are no more small pox vaccines. Thus, there is going to be widespread starvation and epidemics. People in the cities have too many people and no place to get food for them all. Large parts of the Southwest that rely heavily on irrigation are going to turn into deserts. Mountains are suddenly significant barriers. There are no snowplows, so travel in winter just got exponentially harder. What happens to dams and canals and locks and things, now that no one can spare the time or has the wherewithal to take care of that kind of infrastructure? No one has the large scale construction resources to build or even maintain that kind of thing, even if they have the knowledge of old fashioned tech.

In order to get up to 18th or 19th century tech levels, you have to start from 10th or 12th century levels and work your way up. Meanwhile, people with that kind of academic knowledge will be dying off through normal attrition. Just staying alive and keeping what's yours is such a full time job that fewer will have the time, interest or energy to preserve old knowledge. Academia requires wealth to spare. In a world where no one can obtain things they took for granted anymore, there is no wealth to spare.

And yeah, stuff WILL be overgrown fast. You can tell a business is closed down without even getting close enough to a the building to see for certain, just by looking at the condition of the parking lot, and how thick weeds are growing out of the cracks, and if those little tree-like things are popping up alongside the building. And that's after a few months of neglect. With absolutely no one showing any interest or having the ability to knock that stuff back? 15 years and we're lucky there're any signs of civilization.

Which makes the close-to-contemporary mentalities of Charlie, et al. even more annoying.