according to the study, small cars have been responsible for just as many fatalities - or not an amount disproportionate to their number - in the US, so it’s not really big car problem as much as you might suppose. this may have to do with that drivers of small cars can often drive more recklessly, but that’s speculation. And, sure, you can fiddle with your phone with a manual transmission, but, seemingly, most don’t. The difficulty makes it far, far, less likely.
but the biggest takeaways from he study seems to be 1) modern road/highway infrastructure in the US is built to get as many cars moving as fast as possible and give little-to-no consideration to pedestrians or their safety, and this need to change, and 2) the particularly American culture around in-car smartphone use needs to change via far harsher penalties for distracted diving and other behaviors which endanger pedestrians.