In the West:
-Hit Arizona devil's highway, old route 666, one of the best motorcycling roads in the country. Low volume traffic, good pavement, highly technical and very long fun road, 40 miles +. Go fast but pay attention to 15mph signs... they're pretty spot on in those areas. I actually had to stop and collect myself on this road, it's mentally quite taxing to haul ass on.
-Highway 12, via Painted Canyon in Southern Utah, again, phenomenal road. High elevation change, smooth road, wide 2 lane, great sweepers, light traffic. Probably the best vistas I've seen in the whole country.
- Mt. Lemon in AZ. Be careful towards the top, always cops, ridiculously good road, go early AM to avoid rubberneck lookyloos. A ridiculously fun lower 1/2 of the mountain, Dragon-like left-right-left-etc transitions through portions with long 180 bends in the road around the switch backs.
- Anything in Cuyamaca State Park or Palomar Mountain, mhmm, amazing. Watch for ice near Palomar peak top section, amazing road, more for views than speed, too dense to go real fast on most days.
The boarder run across Texas is very long and straight but ... well, if you appreciate history, just think about crossing it on foot/horseback along that path 200 years ago. Yeah, it's boring though (first time I've ever caught myself dozing on a motorcycle was on this road...straight, empty, desolate and was hot AF).