Is it possible for there to be so many more vehicles than decades before that the number of insects hitting each car is much less?

Insects getting better at avoiding cars in a much shorter time than we'd expect would certainly be a prediction of Sheldrake's 'morphic resonance' theory.

The comment above yours was not saying what you're saying.

They were saying, IIUC, that it could be that the same amount of bugs are splattered across a larger number of cars, so that if you look at any one car, then it looks like less bugs.

That was my understanding as well, I was proposing an alternative theory.

There’s a road in my area (rural MN) where I don’t slow down if there are deer on the side of the road. It’s a curvy road with a ton of deer, and back when I was a teenager the deer would do the normal deer thing of potentially getting spooked and run across the road…or directly in to your stopped car.

15 years later they no longer do that, just on that road in particular. I don’t know if it’s evolved behavior or learned, but they absolutely changed.