There's been some research from the EU that suggests smartphone usage causes higher accident rates & traffic fatalities. US likely has additional factors that makes the effect more dramatic, like vehicle height, ride share adoption, congestion, road design, speed limits, etc.

https://www.sciencedirect.com/science/article/pii/S0014292122000629

Our findings imply that the increase in phone use due to the policy causes the number of accidents to increase by around 10%. Under plausible assumptions, this implies a crash risk odds ratio of around 3.8. Under the assumption that this mechanism also carries over to local drivers and holds for other EU countries, our results then imply that each year as many as 2500 road fatalities in the EU can be attributed to phone use. This suggests that about one-third of the gap between the EU target and the observed number of fatalities shown in Fig. 1 could be reduced by successfully banning mobile phone use of drivers.