Well, do you mean tactically, or strategically? Because the army has lost battles before, but never a war out of its own incompetence. Vietnam was lost thanks to political interference.

We will defeat ourselves...Cultures come and go, the same goes for war machines. 'We have met the enemy and it is us'; 'Snoopy' quote I believe.

Good point. Rome was brought down by its own decadence, its own corruption and vice. The Goths merely kicked the structure down. It was already rotten to the core.

More like unable to cope with the demands of its empire, both socially and economically.

Then by definition is America an Empire ? A consultation of the Oxford English Dictionary brought to light this meaning of empire:'Owing partly to historical circumstances, and partly to the sense of the etymological connexion between the two words, empire has always had the specific sense ?rule or territory of an emperor? as well as the wider meaning which it derives from its etymology.] I. Imperial rule or dignity. 1. Supreme and extensive political dominion; esp. that exercised by an ?emperor? (in the earlier senses: see emperor 1, 2), or by a sovereign state over its dependencies.' I believe the Founding Fathers never envisaged America as empire. The English 'Empire' was an anathema to a free society, the 'colonials'(us) knew it in out hearts and took up arms against it. Great Questions!

the US army has been defeated plenty of times. ie. Vietnam

political interferance is the biggest enomy of the US army.

In a democratic state an army exists to be politically interfered with.

Controlled, but some senators back then saw themselves as military leadership types, true? Or was that they believed that our early high-tech weapons could do the job without actually sending in troops to kill and burn. I wasn't alive back then, but I've seen plenty documentaries.

A micro managed war, (vietnam) with too many short strings attached to our army, thinking within the box to some obvious and not so obvious solutions! In short, it would have been a U.S. victory if the occupants of the white house in those times would have commanded less and delegated more. An army restrained berfore an organized enemy, is an eventually defeated army. Or to put it more bluntly, strike often and strike repeatedly. Atleast that's my view!!