If Congress amends Title I of the Highway Beautification Act of 1965 to exempt any area adjacent to any interstate or primary federal-aid highway or any such highway in whole or in part from control of outdoor advertising structures, signs, displays or devices, then such area, or highway or portion thereof, shall be excluded from any regulations by the Commissioner of Transportation for the control of outdoor advertising structures, signs, displays and devices along the interstate and primary systems of federal-aid highways.