My intuition for aerodynamics must not be as good as yours. But looking at https://caradvise.com/blog/2019/08/17/most-popular-cars-in-t... and https://www.caranddriver.com/news/g36005989/best-selling-car... is interesting. In particular, the way the headlights sit on the front of the car seems to have changed a lot. Cars in the 90s look to have lights that pointed straight ahead. That seems to have evolved over time to a more streamlined position and orientation.

It's mind-boggling how many trucks and SUVs this country owns...

It is an variable that very obviously needs to be controlled and is worth mentioning.

Yup, not only that, but the Lamborghini Countach has a Cd of 0.42, while every car on this list has a lower Cd, except for the original VW Beetle [1].

(Although, TBF, the Lambo's wing and aero package adds a lot of drag in exchange for much greater downforce)

[1] https://ecomodder.com/wiki/Vehicle_Coefficient_of_Drag_List

The studies for this are scarce, but this is curious and counterintuitive:

"The research also found that modern cars, with a more aerodynamic body shape, killed more insects than boxier vintage cars up to 70 years old."

https://en.wikipedia.org/wiki/Windshield_phenomenon