Which two wars? Because I think during one of those the Brits may have burnt down the white house and status quo ante bellum isn't exactly kicking *** as the aggressor is it?
\Obvious Troll is obvious.
\\Look, all I'm saying is: War of 1812, didn't exactly go the way you'd planned ya'know? Three years of fighting and no major strategic gains? It's not even like you'd taken them on at home, you were fighting over Canada. I wouldn't fight that hard for like 90% of Canada and I live there.
\\\Everyone point and laugh at Old Hollywood.
Scouse - I'm sorry I really just can't let any of that stand. First, OP is referring to the Revolutionary War and War of 1812 when he says the States have whooped Britain in two wars (He's wrong) you would have to be legally retarded to believe that he would refer to the World Wars thusly. He would have to be legally brain dead to actually say what you think he said.
Second, the American failure in Vietnam was not a failure of combat arms or of influence but a failure of judgment. American arms inflicted disproportionately massive damage against North Vietnam. The US effort in Vietnam was undermined by a corrupt and incompetent local leadership which was barely supported by its own people. Further, US military assistance in the country had the unfortunate effect of organizing the military of South Vietnam as a component of the US military structure. After the US withdrawal and left without a long logistical tail and advanced air force the ARVN was left to crumple as a US Army division would if deprived of all the structures which allow it to function.
Finally the decline of empires cannot be easily extended to the US as the US is not rightfully an empire. It is a Global power that exerts influence in an increasingly connected world and while it's influence will wax and wane we I imagine will not live to see the day when the US has noticeably slipped towards irrelevance.