Possibly because of the rods and chains used for land surveys during westward expansion?
Actually (and I’m trying to make myself look much smarter than I am here), mile comes from “mille pasum”, a thousand paces.
The Roman legions would mark out a thousand paces on their fabulous roads and then mark it with a stone marker (milestone!).
The Legion pace was actually two steps, left foot to left foot (soldier? Remember hut, hut, hut hoo hare four).
Romans were a bit shorter then, and those two steps were about 5 feet, and a thousand would be about 5000 feet, close to our mile.
And back to driving on the right, the biggest impetus was the National Road (today, US 40 in Maryland and Pennsylvania.) It was the first paved highway, made of logs, one wagon wide. Corduroy road.
When you had to pass someone coming the other way, you had to put one side of wheels off the road into the mud and keep the other side on the road. The other teamster would do likewise, avoiding get stuck in the mud.
To avoid having the horse whip hit the oncoming driver in the face, you veered off to the right as you passed.
That’s the sum of my knowledge, as I was in the same study group as Joe Biden.
So I can’t explain why we don’t eat with our forks upside down like the Brits and other Europeans. Maybe that’s why they mash their peas.