Well.... One can only be so precise with today's eqipment.
Secondly, it's not so much military might that wins a war, it's tactics. In Vietnam, we were in a quite crappy time (as well as Korea), with things like "Limited War" and whatnot, that kept us from attacking from other countries, while they just did what they wanted. Hell, we could have just nuked them to death, but we didn't.
Finally, exactly who is it that won WW1, and WW2? If not for the US, Britain would have been demolished.