This fails to pay any attention to how large scale disaster management works. Once things go belly up you will find it is the large cities which get abandoned. Not the small towns. Large cities tend to contain service workers, who are frankly replaceable. Countries need the countryside where light industry, and arable land is.
Like Max Brooks, he also fails to grasp the full range of options available to a serious individual. Weapons wise he is obsessed with firearms, which is nonsense. If you want a quiet weapon which can load anything you like then you have to consider spring power. A homemade airgun which fires ball bearings will do the trick admirably.
Similarly with vehicles he discounts the full range of options. Outside the USA many countries have specialised riot vehicles which you should aim for, like the Casspir.