FWIW, I think that US DOT/NHTSA regulations provide guidance for vehicle
manufacturers and after-market parts makers.
State regulations are enforced on vehicle drivers/operators.
In case you've been wondering,
here's what US DOT/NHTSA have to say,
there are field of view requirements in S5.2.1:
(Current rear view camera proposal not included.)
Nat’l Highway Traffic Safety Admin., DOT §571.111
§571.111 Standard No. 111; Rearview mirrors.
S1.
Scope. This standard specifies requirements for the performance
and location of rearview mirrors.
S2.
Purpose. The purpose of this standard is to reduce the number of
deaths and injuries that occur when the driver of a motor vehicle does not
have a clear and reasonably unobstructed view to the rear.
S3.
Application. This standard applies to passenger cars, multipurpose pas-
senger vehicles, trucks, buses, schoolbuses and motorcycles.
S4.
Definitions.
Convex mirror means a mirror having a curved reflective surface whose shape
is the same as that of the exterior surface of a section of a sphere.
Effective mirror surface means the portions of a mirror that reflect images,
excluding the mirror rim or mounting brackets.
Unit magnification mirror means a plane or flat mirror with a reflective
surface through which the angular height and width of the image of an ob-
ject is equal to the angular height and width of the object when viewed di-
rectly at the same distance except for flaws that do not exceed normal manu-
facturing tolerances. For the purposes of this regulation a prismatic day-
night adjustment rearview mirror one of whose positions provides unit mag-
nification is considered a unit magnification mirror.
S5.
Requirements for passenger cars.
S5.1
Inside rearview mirror. [Not Applicable in this discussion.]
S5.2
Outside rearview mirror—driver’s side.
S5.2.1
Field of view. Each passenger car shall have an outside mirror of unit
magnification. The mirror shall provide the driver a view of a level road
surface extending to the horizon from a line, perpendicular to a longitudinal
plane tangent to the driver’s side of the vehicle at the widest point, extending
2.4 m out from the tangent plane 10.7 m behind the driver’s eyes, with the seat
in the rearmost position. The line of sight may be partially obscured by rear
body or fender contours. The location of the driver’s eye reference points
shall be those established in Motor Vehicle Safety Standard No. 104
(§571.104) or a nominal location appropriate for any 95th percentile male
driver.
S5.2.2
Mounting. The mirror mounting shall provide a stable support for
the mirror, and neither the mirror nor the mounting shall protrude farther
than the widest part of the vehicle body except to the extent necessary to
produce a field of view meeting or exceeding the requirements of S5.2.1.
The mirror shall not be obscured by the unwiped portion of the windshield,
and shall be adjustable by tilting in both horizontal and vertical directions from
the driver’s seated position. The mirror and mounting shall be free of sharp
points or edges that could contribute to pedestrian injury.
S5.3
Outside rearview mirror passenger’s side. Each passenger car whose
inside rearview mirror does not meet the field of view requirements of S5.1.1
shall have an outside mirror of unit magnification or a convex mirror in-
stalled on the passenger’s side. The mirror mounting shall provide a stable
support and be free of sharp points or edges that could contribute to pedes-
trian injury. The mirror need not be adjustable from the driver’s seat but
shall be capable of adjustment by tilting in both horizontal and vertical
directions.
S5.4
Convex mirror requirements. Each motor vehicle using a convex
mirror to meet the requirements of S5.3 shall comply with the following
requirements:
S5.4.1 When each convex mirror is tested in accordance with the proce-
dures specified in S12. of this standard, none of the radii of curvature readings
shall deviate from the average radius of curvature by more than plus or
minus 12.5 percent.
S5.4.2 Each convex mirror shall have permanently and indelibly marked at the
lower edge of the mirror’s reflective surface, in letters not less than 4.8 mm
nor more than 6.4 mm high the words ‘‘Objects in Mirror Are Closer Than
They Appear.’’
S5.4.3 The average radius of curvature of each such mirror, as determined by
using the procedure in S12., shall be not less than 889 mm and not more than
1,651 mm.
http://edocket.access.gpo.gov/cfr_20...cfr571.111.pdf