You might describe ANA as a mercenery force raised by USA and as the catalyst for that force left it has began to fall apart. This raises a interesting question. Why did Pakistan Army not fall apart the British left in 1947? After all the British had raised what was a mercenery army whose units would form Pakistan Army in 1947.
Of particular interest are units like Frontier Force regiment or Guides Cavalry which were raised by British from mostly Pashtun ethnic groups in 1880s. These units built a sterling record and today are regarded as elite units in Pakistan.
I think the reason is FF or Guides had developed esprit de corps over the century [nearly] of British service. Three or sometimes four generations of familes had served these units creating unit esteem and loyalty. Thus when the British left this simply was mutated into Pakistan Army and those traditions have continued to this day. Also there never was internal civil war to break the esprit de corps of these units.
Another unit that is illustrative of the point I am making is Khyber Rifles whose men again are exclusively recruited from Pakistan Pashtuns and almost exact same pool that ANA is recruited from. Again Khyber Rifles has a long history going back over 150 years when it was raised by British. Over the century British military traditions seeped into the regiments institutional memory including using bagpipes as it's standard call. Again this regiment has a long record of battle honours including before and both World Wars.
As a interesting asides to Turkis members here many of these regiments were deployed by Britain against Ottoman Turks and soon were taken out of the line when for the first time they refused to fight or even changed sides.
The bottom line is it would have taken a century to institutionalize their nation building. You can't just tape over a fractious society even if you spend trillions of dollars.
Khyber Rifles logo which is derived from the border pass between Afgfhanistan and Pakistan.
A Khyber Rifles sepoy.
British connection revisited. Princess Diane at Khyber Rifles officers invite.
Raising insituitional military structures not only takes money but time akin to planting sapling and growing it into a tree. In Pakistan most recruits come from various tribes to these units but after a short spell their loyalty is to the unit and not external factors. In Pakistan this why the army is highly regarded because it ensures peace and is the countries backbone. Otherwise Pakistan would also have caved into a catastrophic internal chaos like Afghanistan, Syria or Libya because the social and ethnic composition is very similiar to Afghanistan.