Completely incorrect. The market demand for gigantic cars in the US is virtually insatiable. And will remain so as long as the price of gasoline stays around $2-3 per gallon. Once we see ~$6/gallon like what's common in UK for instance, cars will start to shrink again.
I remember a childless couple that went to a car dealer and got talked into a Chrysler Pacifica (monster minivan) at the steal price of $22,000.
I rode in it and it was the worst hunk of junk, the only car I've gotten seasick in. That car contributed to the implosion of their marriage.
American car makers have a huge incentive to sell 'trucks' because of this old protectionist law:
https://en.wikipedia.org/wiki/Chicken_tax
They make a bigger profit on 'trucks', so they can pay you discounts out of the premium they get.
My brother-in-law has a big-ass pickup truck with a plow attached and he takes a chunk out his big-ass payment by plowing driveways in the winter. He has worked his way up building roads and really does use his 'truck' like a truck.
When I bought a car in 2010 I had no problem finding a small car (industry reeling from 2008.)
In 2018 I went car shopping and found that both Asian and American car dealers had no small cars in stock (the usual state w/ American car dealers) and all sorts of excuses why they didn't.
Right after that they will point you a whole bunch of trucks and SUVs all in a row, all with deep discounts.
Looking at this, I'd conclude that car dealers want to sell big cars, not that people want to buy them.
(A retired ag economics professor I knew bought the $70k corvette that the chevy dealer had for show for $35k at the peak of the 2008 crisis.)