Are American warriors prohibited from winning wars?

There's a great line from a Rambo movie that reflected how Vietnam Veterans felt after the Vietnam war. "Are they going to let us win this time?" The Gulf War not withstanding, America has done poorly in Iraq and Afghanistan. Surely, just as there were in Vietnam, there are many complex reasons for this. I've written and spoken about what Vietnam, Iraq, and Afghanistan have in common--poor leadership from the White House, the wrong strategies, and bad rules of engagement. I firmly believe that no war, save all out nuclear war, is unwindable. America's problem in the post Vietnam War era is that we are unwilling to go the distance and commit the resources necessary to win wars. We won the Gulf War because we employed the doctrine of "overwhelming force." In Iraq and Afghanistan, as in Vietnam, we tried to apply "just enough force" to provide for an exit strategy. Compounding this problem, the rules of engagement stifle the troops. No one wants to stick their neck out for an exit strategy. The situation in the ME and in South Asia may be too far gone to snatch victory from the jaws of defeat, but when will we learn what it takes to win wars? History is replete with examples. Our generals and admirals know them well. Our political leaders who have never served in the military and the American People, apparently, do not.