Google isn't invulnerable in search because of a network effect, which is about your product becoming more valuable because you connect your users to your users (e.g., the Bell System or Facebook). Google is invulnerable in search because search has a very long tail, requiring massive investment to reach adequacy for most users. Google's advantage is economy of scale.

Self-driving cars definitely don't have a network effect. They also don't have the came kind of economy of scale as Google. A person who learns to drive in one, specific part of the US is able to drive, with minor additional learning, in any part of the US. Yes, there's some minimum size necessary to get the data for self-driving cars. But unlike with search, where the minimum size is generally "the whole web", the minimum size for self-driving cars is much smaller. That's why we're seeing many different companies work on it.