Does any company manufacture American AC power plugs with insulated pins?
I don't think so- I've never seen such a thing and if you look at the internal design of a typical receptacle I don't think that such a plug could be reliably backward compatible unless the insulated length was only a couple mm and the thickness very thin. Given the enormous installed base of receptacles and extension cords, such a change is unlikely to be popularly accepted. 

It is possible to get even an adult-sized finger under even a normal plug, so such a design would not pass the UL 4mm baby-finger requirement if it was to be introduced today. 

Here is a photo of an AC adapter plugged into a power bar receptacle. There is 120V present on the pins (verified by voltmeter) and the finger is an adult one (mine, just before my death by electrocution). 



It's worse again if the pins are bent, which is pretty easy with ungrounded cord ends. Especially if some cretin pulls the plug out by yanking on the cord at an obtuse angle.