What amount would these EU fines have to be to make companies like Google and Facebook decide to exit the EU?
probably 15-20% of annual revenue its psychology, the board or ceo would react preemptively based on the idea that shareholders would react on their behalf shareholders (if they have voting power at all) would react for the same result at higher fine amounts than that
1. Other search engines regularly appearing in news / on screens would remind the non-EU users about alternatives.
2. Lost traffic is lost information. Google still relies on knowing your behaviour to improve targeting.
3. Giving a whole region to other search engines would build up their financial standing and they could threaten Google in other regions in the future.