It's a threat to our economy, security, and continuity of business in the unlikely but unfortunate event of a kinetic attack on the US mainland or one of it's territories.
The interconnceted-ness could make perfect sense when it comes to collision prevention. If there is a collision up further ahead, this information can be quickly propagated between nearby cars to warn and/or automatically slow down. I do not know if this is already in use or if it was just one of those possible future scenarios with 5G. Would also make sense if ambulances could make their presence known to drivers much earlier so they can get out of the way.
The problem is that "increased speed" was also "one of those possible future scenarios with 5G". (And with 4G FWIW)
Why do you need a cloud connection for two vehicles 10ft feet apart to exchange data?
Semi-playing devil's advocate since my ideal car is a very simple one. But I can see why the majority of people want various gizmos and doodads in their cars, whether it be a Spotify app or FSD.
So we can show you ads, depending on your car position. /s
Also it is much easier for law enforcement to locate you.