It seems you do not know but there are
TWO equally components in any war: political and military.
The US did not fail the military front in Afghanistan, Iraq, and Viet Nam. In all three cases, it was the politico-socio component that did not turned in US favor. But as far as Ukraine go, do you think the Ukrainians give a damn about Afghanistan, Iraq, and Viet Nam? Do you think Ukrainian generals and soldiers lie wide awake at night pondering if they should give up just because some anonymous persons on the interweb made a flawed argument about Afghanistan, Iraq, and Viet Nam?