Originally Posted by TitaniumAnimations
You can go ahead and think their military is unbeatable. That is what people said when the Roman legions existed, and they were terminated. There is no such thing as an unbeatable army, and while I support the US military, I know that they are not unbeatable. Korean War, Vietnam, Laos, Cambodia, all recent failures, no matter how you look at how the foe won.
Deciding to leave after fighting for a long time on foreign soil =/= foreigners successfully being able to launch an attack on the US.
Think about it this way: if it's this hard for a world superpower to subdue a bunch of guys hiding in holes in the ground, how hard is it going to be for puny third world countries to subdue a superior force?
Oh, and your comparison to Rome is totally pointless. Besides the fact that both America and Rome were powerful military entities of their time, literally nothing else between their militaries can be compared. Not to mention that at the time of its defeat Rome was a decaying society whose army was primarily composed to underpaid mercenaries that had little to no control over its own territories. Any conventional war the US gets in with any single country is a guaranteed curbstomp, period.