It is an interesting thought experiment certainly. We have all sorts of mandated safety equipment on vehicles, so requiring this additional mandate wouldn't be particularly new or different.
It would prevent American drivers from breaking the law.....and would probably a) save lives and b) prevent Americans from getting expensive speeding tickets. So I guess the argument is that Americans should have the ability to decide to break the law, just like robbing banks.
Personally- I love the radar actuated warning signs that alert you when you are going over the speed limit. So how about a compromise- and having those speed limit signs set off an alert in your vehicle if you are speeding. Then if you get pulled over, the car just tells the officer that you ignored the alert and were aware you were speeding?