If you are interested in a deeper dive “Right of Way” by Angie Schmidt is good review of the current research. The biggest issue is the increasing market share of SUVs and trucks which are both more likely to hit and kill pedestrians. Other issues are an increase of poor residents in suburban areas that were not meant for walking, and road design that only considers car efficiency (consider the implications of setting walk sign duration to the average pace of an able bodied middle age male - wheel chair users and the elderly are heavily represented in fatalities).
Mixed use roads can mean a lot of things, but narrowing streets actually reduces fatalities because it serves as a traffic easing measure (see Vision zero).
My personal take is yes part of the problem is infrastructure, and academics who study systems will hone in on that, but the other problem is the complete abdication of personal responsibility in American society. Politicians are too afraid to hold middle class voters accountable for traffic violence or anything else really. The flip side of personal freedom is having to face the consequences of your actions. In some states a DUI conviction does not automatically suspend the drivers license. So I do appreciate left leaning politicians attempting to improve infrastructure, but my concern is these measures are being used to carefully avoid blaming individuals for their actions this laundering society’s terrible driving habits (which I really do think could be changed through social norming and enforcement.
I am very biased though. I’ve almost been hit by multiple cars this year who failed to yield to pedestrians in the cross walk.