> It's a bit fish/bicycle, but the point is, we wanted more people to drive smaller, cheaper, less polluting cars. We didn't want the car manufacturers to find ways of maximising sell, including boosting F150 and F250 class truck sales to mummies on the kindy run.
Unfortunately, the whole thing wasn't built right for the goal. Setting the mpg bar lower for bigger footprint vehicles is on the one side realistic, but on the other side made it hard to build compliant small vehicles. Small trucks in particular disappeared; some say the market wasn't there, but annual sales of the Ford Ranger were pretty decent in 2005-2010 [1]. 2005 was more than the rest, but there were a couple facelifts, and the Chevy S-10 ended production in 2004, so there was probably some spillover from that. (The 2005-2012 Chevy Colorado isn't significantly bigger than the S-10 though). Post the mid 2010s, small trucks basically don't exist, even when small truck names are used. Supposedly Toyota and Subaru are going to bring one back, but we'll see if it happens.
Some sort of special small car class, with benefits, would be needed. Like the kei cars in Japan. Maybe not that small, and maybe not that small of an engine, but that idea of a smaller than normal footprint, but still highway capable, if only just. There is a federal 'low speed vehicle' thing, but the restriction to streets with speed limits 35 mph or less makes it hard to go anywhere in a lot of places. It's not a reasonable alternative to a regular car for most. There's also some recent push to formalize legal use of kei cars in many US states, but federal import restrictions mean they do have to be fairly old (or have expensive and destructive testing), which further restricts the market.
[1] https://www.goodcarbadcar.net/ford-ranger-sales-figures/