World War Z (the film)

[Killer Angel]

The assertation that the US Military is hidebound and working with old tactics is wrong. The US military has for a long time been highly innovative and *flexible*.

Sadly, this is not completely true.
Military history is full of examples of bad tactics, wrong approaches, mistakes, overconfidence, and US military is not excluded.
Every time people tend to think that the current army is led by brilliant mind, and often that's true, but in every army you'll find high officiers not able to adapt.
Let's pick only the (relative) recent history.
DUring the american civil war, it appeared that applying a napoleon-like formations, marching toward well defended positions, was not a good idea. Manoveurs were far better, and yet there were lots of examples of frontal charges against trenched positions.
Was the lesson learned in WWI? nope. The formations were abandoned, but there was frontal assault to trenches, barbed wires, machine guns' nests.
There are examples of massive frontal assault of infantry even in WWII.
Of course army is innovative and flexible. But sometime you don't "see" that you're staying behind. At the begining of WWII, many failed to see the power of air force and tanks' manoveur, and put their faith in fortresses. Anzio failed due to poor decisions after the landing, and so on.
After WWII, someone discovered that you cannot successfully apply WWII tactics to an enemy that uses giungle guerrilla.
When US army had become invincible on an "army" scale, still you can see total failure in planning rescue operation such as Eagle Claw.

Every army will commit mistakes, due to bad planning ad overconfidence, every army has its Little Big Horn. So, Yonker will happen.
Only, it won't happen in the way described, because you're going to fail while applying a current tactic (such the actual ones in dealing with popular riots, or the ones used in urban warfare). Actually, no one is seriously going to dig trenches.