Earlier quoted context omitted.
I'm honestly surprised they don't restrict that. Does anybody know why? I know different states have different speed limits, but I think a 85mph speed limit could cover them all. Is it because Canada and Mexico? They have lower speed limits. Is it because the car could be exported to Germany and driven on the Autobahn? or what?
The main reason car companies don't put (un-overridable) governors for 85mph in cars is that their sales would instantly plummet. That said, all "fast" cars sold in the US do have governors at 140 mph if memory serves. The same car sold in Germany has no such governor.
They circumvent this with their own car tuners which release the cars without this restrictions (AMG for Mercedes Benz as an example)