An autobahn isn't feasible in the US because the domestics would actually have to man-up and build decent cars! Not to mention, all American drivers would have to go through drivers ed again, or the fact that we don't have the money for such an infrastructure expense. "Don't you know there is a war going on?"
American cities are not in close proximity to one another, like in Europe, so motorists would be driving at 100mph+ for hours on end. This sounds good, but I suspect that many cars are not 100% perfect mechanically, compliance would be expensive and difficult to enforce. Environmentalists would carp that it is a waste of fossil fuels, etc..
I've seen the HC show twice; I like Germany's method of enforcement.