Why is the US so slow in crushing enemies in the Middle East?

Many armies capture either by storm or by siege warfare.

This is what the US did in Kuwait, battle of Baghdad, and in Operation Neptune Spear.

This is what the Turkish army did in their invasion of Afrin, and what the Syrians did in their attack on Ghouta.

But how come the US doesn't do this more often?

Why waste so much time in these delaying Fabian strategies when the army should just storm the city?

And why does the US army prefer to work with Kurds and mercenaries rather than deploying its men to the theaters of war?

I never understood this idea of "let's train and give arms to the rebels"

You will notice that the Turkish and Russian armies aren't really pro mercenary as the US. Why is that?