The military vehicles electronics are heavily shielded against EMP. Basically, an attack of immense power will bypass shielding of any type if you are too close to the source. Nuclear detonation at 10000 feet about our country, one over Colorado and one over about Tennessee would effectively shut us down. Russia still makes a lot of tube powered items, because they aren't an affected technology. Primarily, only semiconductors or certain types of diodes are affected. Such an attack would hurt a lot more things than people think. Every television, radio, cellphone, computer, post 1975 or so vehicle with electronic ignition or an alternator, many heating furnaces, air conditioners all dead. System failures would include many sewer, water supply routing, electric grid supply generators, air control towers, most planes would just drop. Not a pretty picture.