Yes, American generals are not smart.
Let's take a recent example, Afghanistan, how did Americans attempt to conquer the taliban? Murder anyone and everyone that's with them, they won the battles, they have lost the war. British had the right idea of trying to get hearts and minds but this had limited effect.
Vietnam, how did Americans try to win? Bomb them into submission and send in a ton of forces, once land based warfare failed they went for kill count to win, they lost.
American soldiers and generels rely on "We have more men then you do." We know this as when Montgomery was commanding American tank units they were terrified of fighting the enemy when they had less men, Montgomery convinced them that their quality was superior and was able to use their strenghs rather then their numbers, which was what the Americans relied on during world war two (and in part their industrialisation.)