Afghanistan was a mess for reasons other people have mentioned, but the US held itself back. If you want to see supremacy see Desert Storm. The ground campaign took 100 hours for the US to kick the ass of the fourth largest army in the world, not even mentioning the beauty of the air campaign. It is a master class in the brutal efficiency and warfighting capabilities of the US and other coalition forces. If the US wanted, there is no doubt they could have razed Aghanistan and Vietnam from a pure warfighting standpoint.

Technological and logistical abilities still reign supreme if it comes to an all out war. Asymmetric forces like with Aghanistan and Vietnam were problematic because of political pressures at home, and the long drawn out nature of those conflicts which increased political pressure. The 2003 invasion of Iraq was also perfectly executed, but the long duration occupation was the problem.

Asymmetric forces and insurgencies are problematic, but people overate them in modern discourse because of the weight of the occupation of Aghanistan and Iraq in recent memory. They are easy to crush, but politics at the time was complicated.