Yes, but in Texas you'll find the interstate speed limit is 85 and in Ohio it was 65, now it's 70.

There's not some fundamentally crazy difference between Ohio and Texas roads that results in Texas accepting 20mph higher speed limits than the rate Ohio was using within the last 10 years or so.

There is a history of speed limits for fuel efficiency and scarcity https://en.wikipedia.org/wiki/National_Maximum_Speed_Law. Which is more evidence that speed limits do not inherently correspond to safety. Driving the limit, over the limit, or under the limit doesn't "magically" make you safer.

Sure, if you're in an accident two objects traveling faster are going to cause more damage to each other than two objects traveling slower. However, getting into that accident in the first place has little to do with speed and a lot to do with situational awareness and giving yourself enough time to stop in case of emergency (i.e. how close you're following the car in front of you, how fast you're passing kids on the sidewalk, etc).

You'll note speed is always blamed for increasing severity (i.e., it's a factor in the severity of the accident). Unfortunately the links don't work anymore to get to the underlying source but https://sites.psu.edu/siowfa15/2015/09/18/is-driving-faster-safer/ states "A study conducted by the Florida Department of Transportation says that accidents that were caused by speeding is actually 2.2%." The Autobahn is another great example. Speed is very rarely cited as the primary cause ... because speed isn't really the issue.

We should be focusing on issues that actually cause accidents like tailgating, blocking the left lane, failing to signal, etc.