One significant effect of the creation and dissemination of the Kalashnikov was the utterly woeful development of America's M-16, a rifle that proved utterly useless in Vietnam due to what seems to be nearly constant jamming problems caused by shoddy manufacture. Though it's a weapon that eventually proved its worth after considerable modifications, in its initial form, it was profoundly negligent to allow it anywhere near a battlefield.
After McNamara's team endorsed the assault-rifle concept, the United States military could have decided what it wanted an assault rifle to be and to do. This would have been a matter of proposing specifications for caliber, muzzle velocity, weight, accuracy, and any number of other characteristics. These specifications could then have been provided to government designers and private industry — to Ruger, to Colt's, to Remington, to Winchester, to Browning, to Cadillac Gage, and others — with a deadline for design submissions. In doing so, the intellectual capital of the private sector would have been invited to compete. And when the deadline came, the Pentagon would have had multiple designs from which to select. Instead, the United States had a hyped rifle rising through the bureaucracy with little testing or vigorous competition. Its selection process looked less like deliberation than lunging. And as McNamara and General William Westmoreland pushed and pulled the rifle along, the signs from tests and field reports of its emerging weaknesses were suppressed. Colt's assault rifle, the internal reports said, was vulnerable to corrosion and given to malfunctions. No matter. The most senior military officials knew American troops were being outshot. They ordered the M16 — as the military's version of the AR-15 was named — first in a batch of 104,000, and then as the standard firearm for the war. The rollout began.