So you're saying that 26% of British drivers don't have a license?
No, that was a typo. Someone already brought this up in a reply before yours. I was referring to the percent of Brits with licenses.
I'd say that per sq mile of road there will be more cars in the UK than the US,
On average I could see that as we're a very spread out country. Our major urban areas have far more drivers on the road at any given moment though.
Also, driving behavior varies by where you are in the US. The North East is known for its aggressive drivers where as where I live in Northern California the drivers are almost too polite to the point that they'll violate right of way rules and create roads hazards just to be nice and create a spot for you to merge in for instance.
The last example is super annoying too as since they arent following the rules of the road the person they are trying to help then has to figure what the heck they are doing which generally creates more delays then if they had just followed the rules of the road and driven by. This happens to me once or twice a month where I live but would almost never happen in the North East.