I had the same questions myself. I tried to follow the citation on wikipedia, but that links to a newspaper article that doesn't seem to mention it at all.
Edit: on the other hand, the claim "meta-analysis by Rutgers researchers found that Permanent DST would eliminate 171 pedestrian fatalities (a 13% reduction) per year.", does actually link to a paper: https://www.sciencedirect.com/science/article/abs/pii/S00014...
North America does seem to like their cars, and is quite hellbent on finding any explanation for deaths caused by automobiles that absolves the system from having to take any responsibility or do anything (e.g. build infrastructure, regulate cars, etc.).
Of course, that's not to say that six school children being killed by motorists didn't happen after the time _didn't_ switch, but to pretend that the preceding week or two were materially different in terms of light / dark levels to the degree that driving was significantly more dangerous would mean we have to accept that certain hours at certain times of year are always more dangerous (and we should then enforce more restrictions on when one may drive).
If the idea that not switching to driving an hour later causes more dead children sounds preposterous, then DST seems to be a straw-man being propped up. More likely: there was general unhappiness about the change, and people were motivated to find a reason to repeal the law (and cars and bad car-centric planning came in to save the day). It's very easy to take the wind out of a political movement for change, but not necessarily to put them back in. I've been meaning to read Jessie Singer's new book [1], and this seems similar in that regard. Rather than acknowledge that our society has built things (e.g. bad infrastructure) that cause harm (six children died) we instead point at the problem and any attempt to make change anywhere in the system is looked down upon because that would be interacting with the problem, which makes you responsible for any effect of it down the line [2].
Overall, I think my take-away is that we know that shifting the clocks twice a year causes some non-zero amount of suffering (and doesn't have a large justification for _why_). Rather than "Chesterton's fence" ourselves into inaction, we shouldn't let past reasons dictate our choices here. There's surely a lot of overhead with regard to making this change (my heart goes to anyone who has to work with international date / time APIs), but even with knowing that I still don't think it's a bad idea. A unanimous vote by the US Senate surely says that there's some will towards doing this, since it's rare for anything to be this bi-partisan nowadays...
Also from your link:
> In the state of Florida alone, at least six school children were killed by motorists due to the dark mornings created by the new law.
I wonder how in the world they attributed that to DST?