Having lived here for 10 years now, I've come to the conclusion that the average American driver is desperately afraid of G-forces.
The slightest bend in the road will cause the brake lights to come on, as will any slight change in road condition - a difference in the crash barrier, construction cones, a bump, an different road surface.
I've seen maybe 1 in 1000 drivers actually accelerate away from a green light. The usual method of doing this seems to be to gently rest their foot on the accelerator so the car creeps up to 25mph over the course of 30 seconds or so.
Worse still, when traffic lights go red, they start braking a good 100m ahead of time, drifting idly to a halt.
I can only surmise that this is because they don't like G-forces. Acceleration, braking and cornering all cause you to be moved around in the driver's seat and it seems like no American likes this. Why else would you go around a corner with the brakes on? Brake before the corner, then lift off the brakes and turn - it's not that difficult. If you're braking and cornering at the same time, you're overloading the tyres and asking them to split their grip between slowing you down and keeping the car in the corner.
Freeway intersections are the worst - when you have a large-radius, curving flyover to go from one freeway to another, you should be blasting around that at freeway speed to keep the flow of traffic. They're designed specifically for that. But no - everyone slows down to 40mph and ambles along to the point where - on a motorbike - I've been able to slalom between 8 or 10 cars on a single overpass. With plenty of room too - not cutting anyone off.
Given that G-Force seems to be the issue, lightweight, small-capacity cars are what America needs. 800cc two-cylinder engines in little shopping commuters. V8s, V6s, turbos and superchargers are all wasted in this country - nobody uses them. Low-profile high-grip tyres? A waste of time. Lowered sports suspension packages? Useless.
From a European's perspective, it makes me look like I'm speeding everywhere I go when in fact I'm doing the limit. Everyone else is just driving too damn slow.