The first real blemish on the so-called American Century was the war in Vietnam, where the greatest military force the world had ever known was bogged down for years fighting an army of indigenous insurgents who could blend in with the local population at will.
The current version of the greatest military force the world has ever known has been bogged down in Iraq and Afghanistan for years, fighting armies of (largely) indigenous insurgents who can blend in with the local population at will.
The American Revolution was begun when indigenous insurgents who could blend in with the local population at will bogged down and harassed the greatest military force the world had ever known.
The parallels can’t be pushed too far. The Viet Cong won because American public opinion turned against the war; they were routinely hammered on the battlefield. The American colonies were eventually able to build an Army that gave the British enough of a beating for them to go away. We’re likely going to be able to declare victory and leave Iraq and Afghanistan on more or less our own terms, though who—or what—will fill the vacuum is unknown and worrisome.
Still, it’s a little disconcerting, and worth noting to anyone who complains because these rag heads won’t fight fair.