There is the classic set of pictures showing how much space is needed to transport 60 people by bus, by bike, and by car.
https://humantransit.org/2012/09/the-photo-that-explains-alm...
On my (pre-covid) morning commute to the office, most of the cars crawling along the highway had one person in them. The slowness is the result of people trying to merge into the highway, not "bad drivers".
Another way to illustrate how much space cars take up is to look at suburban office parks. There will be a small building (usually 1 or 2 stories) surrounded and dwarfed by a parking lot.
https://usa.streetsblog.org/wp-content/uploads/sites/6/2014/...
https://www.google.com/maps/place/Liberty+Lake,+WA/@47.67315...