Alphabet trades at a forward price-to-earnings ratio of 19 times next year's earnings estimates for the world's most dominant search company, a fast-growing cloud computing business, and a leading streaming video platform. At this point, Waymo is largely an afterthought that isn't reflected much, if at all, in its valuation.

The U.S. robotaxi landscape is mixed as cash-burning startups struggle to move from on-road test fleets to commercializing in a handful of cities.