Isn't that 95% of California? Or America in general for that matter?
"America" has continuous mountain ranges from Patagonio to the Arctic circle. The state of Alaska, alone has more and taller mountains than all of Europe. The NW states of Washington, Oregon, Idaho and Montana along with British Columbia contain the Cascade and Rocky mountains which rival anything in Europe. No cities, interstates or heavy traffic exist there. California has great roads North of San Francisco and NE of LA. The Tour of California was obligated to ride through their sponsor's neighborhood. That's Amgen and Specialized which are pretty much based along Interstate 5.
I think the last T of C include hilly areas that Jens Voight has his fondo. They are gorgeous, narrow and frightening to descend with bad pavement. One stage descended to the mouth of the Russian River connection to the Pacific at Jenner. Levi Leipheimer rode to the front and gave the whole peloton the "chill out" signal because of the sudden 20% sections. Most of the pros hated riding around that region because it was too hard for that time of year.
Lovely roads to ride with few people, houses or cars.