Using a horse for bareback transport. Riding it until it goes lame and then eating it isn't part of any ferrier book I've read. Yes, they traded for guns, stole guns and scavanged guns but where are the mines, the forges, the machines needed to make the guns?
If you'll take a good look at conditions on the East Coast at the time, most of the technology you identify was actually located in Europe. Guns were, for the most part, imported. Eventually mines, furnaces, foundaries and so forth were built in America and the people there went out and conquered the Earth. Took about 100 years to do that though.