I'm absolutely relying on anecdotal evidence. But I spent more than a decade on tour with a band driving vans all over the US and Europe. I've been on almost every stretch of highway in Germany and America many, many times, and I was extremely familiar with travel times between cities in all seasons and conditions. So yes, still anecdotal evidence, but a whole lot of experience behind it.
Obviously construction (anywhere) affects travel time. But in the US the highways have more exits, cops running radar, and there's ALWAYS someone going slowly in the left lane. Unless you're in the western desert states, it's pretty hard to maintain a steady speed. By contrast, everyone in Germany knows how to drive, and everyone follows the rules about keeping right and passing left.
Obviously construction (anywhere) affects travel time. But in the US the highways have more exits, cops running radar, and there's ALWAYS someone going slowly in the left lane. Unless you're in the western desert states, it's pretty hard to maintain a steady speed. By contrast, everyone in Germany knows how to drive, and everyone follows the rules about keeping right and passing left.