I believe the main reason for why European trucks look soi different is regulations. European trucks have a length limit that covers the tractor as well as the trailer. Because you want to maximize the cargo space, the tractor is made as short as possible and gets this very un-aerodynamic shape. The truck in essence gets the shape that best fills in all permitted space. In addition they don't have plows or similar that make them take less damage in collisions because Europeans instead minimize the damage to people hit by the truck. Given the US doesn't have those regulations you really need different trucks and one truck won't work in the other market.
Just to clarify, cab-over trucks are still being used today in the US, though most new ones are smaller cargo-sized. From time to time, I've seen existing COE trucks used; but mostly for private farm use (as they're not nearly as popular as they once were here, and are getting long in the tooth).
The engine sticks out in front the driver cabin. They also don't have barriers on the side that keep passage cars from getting under and being hit at head height
