>My wife says it may be a dangerous thing to do in a country with so many >guns around, where "road rage" is a known sociological phenomenon.

There is always the risk of retaliation, but I would worry less about the guns and more about the law. I'm pretty sure that in most states, reacting in the manner is illegal. You'd have to check.

>Generally, what does a normal American do, short of bying electronic tinting for the mirrors and other protective toys?
>

Regardless of the size car you drive, there is ALWAYS somebody on the road whose lights will annoy you. Most of the time, I change the mirror angle; most cars have a lever on the bottom of the mirror to do this, but occasionally I'll physically move it. If the offending vehicle has the high beams on, I'll flash mine at the car once it's past. But, I admit, I will give them a good dose if I think they are being a jerk.

Of course, nobody has ever accused me of being "normal"...