The Army became "unbalanced" since 2003 as it adapted to fighting insurgents and terrorists rather than other conventional armies. The Army faced the same issue in the 1970s as the Army was pulled out of Vietnam. Looking at that transition from COIN Army to conventional Army is useful.
The Army has one main advantage now as opposed to the 1970s. America didn't destroy our Army during the Iraq and Afghanistan campaigns.
After Vietnam, our Army was basically broken. And it isn't that we lost the Vietnam War. Arguably we won that war, decimating the Viet Cong as a local force of resistance and holding off the North Vietnamese Army. Sadly, we didn't support the South Vietnamese armed forces we built and South Vietnam succumbed to a conventional North Vietnamese invasion. So it seems like we lost.
We avoided that problem in Iraq despite a premature exit in 2011 by re-intervening in Iraq War 2.0 in 2014 following the ISIL uprising. And in Afghanistan we have arguably avoided that problem by reversing the planned departure which could have left the fragile Afghan government in peril of falling to the Taliban.
But honestly, even if Iraq had fallen to ISIL and if Afghanistan falls to the Taliban, the United States Army would still be in good shape as an experienced force, albeit unbalanced. It has a sound foundation of battle-tested troops to balance for conventional warfare.
The key difference isn't victory or defeat. The key difference is that the Army learned from the Vietnam withdrawal that breaking unit cohesion is the way to break an army.
In Vietnam we rotated soldiers and not units, and in the withdrawal grouped soldiers into units based on their time in country in order to "be fair" to soldiers. The idea was that withdrawing a unit with a soldier there just a week while leaving a soldier who had been fighting for 10 months but in another unit was "unfair."
That was a stupid concept and the constant churning of soldiers in units, as units were pulled out, turned our army into a collection of armed men wearing the same uniform. The often draftee troops resented the leadership which had declined as casualties rushed training, used drugs, and lacked discipline. That broke the Army.
In Iraq (and I assume in Afghanistan) we rotated during the war and then withdrew during the draw down units and went to great lengths to maintain unit cohesion--including extending terms of service for soldiers so they didn't leave the service before their unit came home from Iraq.
That was not a "backdoor draft" as critics charged, by a way of keeping the Army effective and lowering casualties by maintaining unit cohesion.
Even if we had a drafted Army for the post-9/11 campaigns, I think that unit
deployment emphasis would have kept the Army intact as a fighting force in contrast to Vietnam.
Anyway, as the Army goes down the same path of refocusing and re-equipping its forces from a COIN focus to a conventional warfare focus, the Army has a better foundation of quality volunteer soldiers and unit leaders than it had in the successful transition begun in the 1970s which proved its mettle in 1989 in Panama and in 1991 in the Persian Gulf War.
Initially trained in 1988 and 1989, I like to think I was part of the pinnacle of the Army as a conventional combat force. :-)