> If trucks were designed for aerodynamics, shouldn't one of the designs have "won" by now,

Because aerodynamics is not the only concern the manufacturers are thinking about.

The difference is in the regulation. The maximum allowed length for a semi-truck is shorter in the EU than in the USA. And since they both want to transport the same length of container the European truck had to be designed shorter.

My dad used to drive concrete delivery trucks in europe. Most were the european arrangement with the cab over the engine, but one of them he drove had the American style long-nose. It was so unusual that they nicknamed the truck after this feature. They called it "csőrike" which is hungarian for "the one with the beak".

He also said it was a lot easier to maintain the long-nosed vehicle. With the european cab-over design you have to first secure everything in the cab and then tip the cab forward to have access to the engine and transmission. While with the long-nosed concrete truck you could just open the hood and get to work.