I don't think that's it, Kevin. American drill is especially good for what it does which is its simple and works well for large formations of troops who haven't been drilled to death. It's an outcropping of the US military's general attitude that: "parade square drill isn't the sign of a professional soldier, its what we do in the field that matters."
Any small drill team that practices for weeks for an event will look good even from the most slovenly of armies.
The drill for trooping the colours is antiquated, designed to manoeuvre forces in 1800s close formations. - Really! Who needs to do a right form for anything anymore - whether on the move or at the halt? It's designed to make people appreciate the ability of individuals to act as part of a unit. You don't need to stamp feet, but you need to be in step or in sync in other motions.
You want to see Brit drill done to the ridiculous, watch Indian or Pakistani troops some time . . . or any of the Brit based Caribbean or African forces.
The difference between good US drill and poor drill is founded on marching in step and looking like a unit with pride as opposed to shambling along as a group of individuals who look like many of them would rather be somewhere else than.
Leather shoes and horse shoe cleats are a great thing for a soldier to hear in order to get the rhythm of the march when its otherwise quiet. Troops in softer gear get the same thing from having a band play or even a single drummer beating the pace. That's an organizational flaw. Who can march properly when the speakers are blaring out rock music? Honestly WTF?
I don't want to de-emphasize practice. You're bang on - the longer the practice under properly motivated NCOs, the better the "performance" is. Watch a video of US Marines at their graduation parade some time. I have zero idea how much the folks yesterday were picked and trained for this parade. It seems like several hundred from each division attended. A division has some 15,000 folks in its. Surely out of 15,000, the respective command sergeants major could have selected a few dozen from each unit that could march and hold a few rehearsals on how to march as a unit.
Yup. I agree. We can and should do a lot better.
I tend to think we have a problem in that we put priorities on everything and we're currently at a point where we do not want to spend time or money on looking good on parade. IMHO parades are like any military function; you need to train for it to get good. Priorities determine where you spend your time and money.
OTOH, it shouldn't take long to organize, train for and conduct a simple parade. And let's face it most of our - and the US parade yesterday - are simple parades. Change from line to column with a simple turn and march in step. That's not rocket science by any stretch of the imagination . . . especially with a proper band. Attitude has a lot to do with it. Back in my onion on the belt days I recall that our parades were of two types: those where we couldn't give a shit no matter how hard the RSM drilled us - change of command being a simple example - or those where we wanted to strut our stuff and impress the audience - freedom of the city parades being one. Like anything; you have to grab the morale of the troops to want to be there and do their best. That's missing all too often these days.