In Canada I get 70km/hr max if it does not know the speed limit. If it does, then I can set it to what I want. It mentions this in the manual under auto steer.
How do you set it? This is what the manual says in the USA...
Restricted Speed
Autosteer is intended for use on freeways and
highways where access is limited by entry and
exit ramps. When using Autosteer on
residential roads, a road without a center
divider, or a road where access is not limited,
Autosteer limits the driving speed. The
maximum driving speed is calculated based
on the detected speed limit plus 5 mph
(10 km/h). In situations where the speed limit
cannot be detected, speed is limited to
45 mph (70 km/h). When Autosteer is
engaged in these situations, it reduces your
driving speed and your set speed to be within
these limits. You can manually accelerate to
exceed the limited speed, but when you
release the accelerator pedal, Autosteer slows
Model S to the limited speed. When you leave
the road, or disengage Autosteer by using the
steering wheel, you can increase your set
speed again, if desired.