European countries have higher speed limits than the USA. Some states in USA have terrible, slow moving drivers that you see signs posted for minimum speed limit (Florida, South Carolina). There are people who literally drive 35m on left shoulder and blocking traffic. I take Interstate every day for work, and the demographics for slow moving drivers are generally well known. In rush hour, the traffic is literally bumper to bumper and I drive 12 miles for one hour in some cases.
If anyone complains about the speed, he or she should try German's autobahn with extremely high speed. I did not have a speeding ticket for 20 years, but if the speed limit is 55 to 65 on interstate I will be driving it. There is no reason except if there is weather problem or a visibility issue to drive below the speed limit. The worst drivers in USA in experience - Seattle, Florida, and Maryland. Nothing worse than driving between Seattle and Tacoma, and everyone is driving 40mph. Florida with elderly population is a chapter of its own. Even local roads have posted minimum speed limit, because people are literally matching there the speed of bicycle.