Nah, we know this isn't the reason because in other countries that have better road design that actually takes psychology into mind for design speeds, they did not see the same uptick. Also, other countries are seeing gradual decreases in road deaths while the US continues to see increases.
You can also look at e.g., the dangerous by design reports and see very clearly WHERE the road fatalities are happening. During covid it was all over the map. Post covid, it is clearly skewing away from the blue cities.
It's a very clear natural experiment with an obvious conclusion: the US has fundamentally unsafe road engineering. We focus on speed over safety in our designs, which in low congestion works perfectly (i.e., makes roads fast and unsafe) and in nominal conditions achieves neither.
Load up all of AASHTO into rockets and shoot them into the sun.