A study of American history would prove that country has not had a good record of winning wars. That's with all due respect to the many who gave their lives in the First and Second World Wars.
The war for independence from Great Britain was a brilliant series of guerilla battles.
Thus was the infant republic established. After that it was all downhill, with the notable exception of the short-lived Texan republic's struggle to be independent of Mexico.
As for the calamitous Civil War of 1861-65, Abraham Lincoln recognised the genius of Virginian Confederate General Robert E Lee from the outset and is reputed to have offered him 1 million to take command of the Union forces.
After that came the stalemates of Korea and Vietnam. So how long must the Afghanistan war drag on?