I find the claim that the USA went to the 9mmP to comply with NATO to be lacking believability. The first NATO standard cartridge was 7.62X51. A cartridge forced on NATO by the USA. When the USA decided to switch to the 5.56 M193 round it too was forced on NATO.
Meanwhile, since 1911, the USA has been issuing the 1911/1911A1 in .45ACP as its' standard military pistol. No other country was complaining that we had the 1911A1 .45ACP. The pistol is of very minor consequence in warfare. I would guess that of all the wounds received in combat, less than 0.5% are from pistol rounds. Probably closer to 0.05%.
The 5.56 M193 round was noted for delivering horrendous wounds that put a belligerent down right now. Why? Because, from a 20" barrel the 55gr. bullet yawed and broke in two larger pieced and hundreds of tiny pieces. Blood flowed from so many wounds that blood pressure dropped and so did the bad guy.
Then soldiers complained that the 20" barrel was too long to maneuver in tight quarters, a valid complaint. The M4 was the solution to this problem. However, the M4 should never have been the general issue weapon. The bullets are just too slow to yaw and fragment. So, let's get a heavier bullet right? It goes even slower, is heavier constructed and fragments even less. HMM. So now we are issuing a 77gr bullet. The slowest yet. But it is doing a great job. Why? It is of very light construction so at its' reduced velocity it will still yaw and fragment.
We just needed to stick to the 20" barrel and the M193 cartridge for general issue and the M4 for those doing house clearing.
As for accuracy, the 20" M16 kicks the M14s ass at EVERY distance at Camp Perry. Sure, it is not combat but it is ACCURACY.
Just cut the M14s barrel back to 14.5" and watch its' power and accuracy decline.
For myself, after owning an M1 Garand, M14, L1A1, extensively using an HK91 and owning a Mini14, I will stick with my 20" AR15 and M193 ammo.
After 150,000 rds (approximately) through my beloved 1911A1, for use when the balloon goes up I will not be carrying it. I will be carrying its' wide body cousin, the Para P14-45. Same lovely cartridge, ergonomics, internals, just 14/15 in the mag instead of 7/8.