If America is so bad at using its power to achieve victories, how is it that we remain by far the most powerful country in the world?
I don't understand why people keep asking why America can't win wars any more. Amazingly, that entry in the genre expands the list of American disappointments to any problem of violence or potential violence anywhere in the world.
Honestly, how can victory in Iraq not be recognized?
But that failure to recognize American victory is a general failure (with a corollary that enemy "victories" are judged with a low threshold), which is probably due to our very open society.
Victory is generally just the entry ticket for the next problem to solve. Don't get stuck on visions of victory that are beyond mere mortals--even the only superpower--to achieve.
We're doing all right, all things considered.