Top rated answer:
In more or less decreasing order of importance, why America cannot handle high-speed autobahn-type freeways:
1.Car control. It's too easy to get a driver's license in America, i.e., formal car control courses are not required and are required for speeds greater than 70 or 80 mph / 130 kph. Car dynamics change radically once you start to exceed 90 and 100 mph / 140-160 kph, especially with respect to suspension (bumps) and aerodynamics, especially in cars that aren't properly designed for high-speed driving. To wit: it is far more difficult to get a driver's license in Germany.
2.Driving etiquette and rules. In addition to formal car control classes, proper driving etiquette and rules need to be enforced beyond merely "signal to switch lanes," "look over shoulder," etc. For example: "left lane for passing ONLY." A big reason the autobahn works in Germany is because people religiously obey the lane rules: you keep as far to the right as possible, and use left lanes for passing ONLY.
3.American culture. Most Americans' mentality towards driving cannot handle the far greater responsibility required by higher speed limits, let alone derestricted stretches of highway. Combine this with a general sense of entitlement (think large SUV sitting in the passing lane doing 55 mph while surrounding traffic is doing 65) and part of the problem is clearly cultural.
4.Road construction. German autobahns are an engineering marvel of road surface construction: they are unbelievably well maintained, smooth, and with none of the poorly constructed undulations, bumps, and dips of American freeways (at least here in California). Further, they are all made of asphalt / tarmac unlike the recent trend (in California) of using noisy, low-friction concrete which is basically useless in the rain.
5.Service stops. German (and many European countries) freeways have awesome "pitstop-like" gas stations: you don't have to fully exit the freeway, rather the station is on a sort of pit road alongside the freeway. This makes the entire freeway process -- especially on long road trips -- a far more efficient process and adds to the whole package.
There's a reason why during my travels in Europe, and Germany in particular, I saw far fewer near-accidents and witnessed far fewer ignorant drivers as I cruised along at 220 kph / 130 mph than I do on a daily basis here in California at half that speed.
Next answer:
Many reasons:
1.Germany is actually the only country in the world to not have a speed limit, and that lack of a speed limit actually applies on very very few roads.
2.The process of getting a German driver's license is notoriously difficult and expensive. Meanwhile some US states have very liberal laws on this matter.
3.Liability laws are different. Say for instance you jaywalked and a car crashed into you and killed you. Your estate would be liable for the repairs and medical costs to the injured driver and their car.
4.Sense of entitlement is different. Germans tend to approach the rights they have not with entitlement. For example, there is no law against drinking alcohol on the street, and you can in fact consume alcohol in virtually any public place unless explicitly stated otherwise, however, if you make an a** of yourself prepare to be arrested. It is not their right to drive as fast as they want, it is a privilege which can be revoked any time if it gets abused. This is one of the things that make Germany a fantastic place to live.
And this one is particularly interesting. Sounds like there is actual political weight TOWARD driving enthusiasts. Well, that is just insane.
Almost no other country nowadays has unlimited speed highways. It is a peculiarity of German culture.
Americans love powerful guns. We love powerful cars.
The NRA has 5 million members. In comparison, the ADAC, Germany's automobile club, has 18 million! That is almost a quarter of the population. They have had their scandals, but these guys are solidly mainstream and have some serious influence in German politics.