“Americans have all the watches, we have all the time.” Words of a captured Taliban fighter.

Quora Question Why do people say America has the most powerful military …

Quora Answer:

Is it fair to say that the US military is the best in the world at taking down any other military force. Iraq? When it still had a conventional military force that even tried fighting back, it was a duck shoot. US forces trounced them so thoroughly that no conventional military force will attempt to engage them.

But conventional military force is only useful if you need to dismantle another military force. It’s super-effective at winning battles!

…but there’s more to winning a war than just winning the battles.

Wars have political objectives, and if the objective isn’t just knocking down an opposing force, it’s a bit like having a hammer when you also need a screwdriver (and screws, and other sorts of fasteners, etc). You’re equipped for part of the project, but not for the rest of it.

The reason we “can’t seem to win any wars” is that our military isn’t facing any conventional military forces, they’re engaged in lots of unconventional/asymmetric warfare, and that neutralizes a lot of their advantages.

But more importantly than that, they’re tasked to fight in contexts tilted heavily against them; they are as often as not seen by the locals as illegitimate occupiers, and their opponents are able to use them as cover (and to recruit from them; locals angered by collateral damage inflicted by US troops and tactical strikes are a huge resource advantage favoring insurgents):

Americans have all the watches, and we have all the time. “Time in jail and time in the jihad mean nothing to us. … Your watch’s battery will run down, and its hands will stop. But our time in the struggle will never end. We will win.”
– Mujahid Rahman Afghan fighter, Newsweek, 2011