To be fair: The United States hasn't declared a "war" since 1941. All other military actions since have been military resolutions endorsed by Congress or undeclared police actions with no political backing whatsoever. Even then, the author is cherry-picking. We "lost" Vietnam but we "won" the fuck out of Granada, Panama, Nicaragua, Croatia, Libya, etc.
To "win" or "lose" has to be judged in the terms of the conflict, not in the terms of WWII. Most every boots-on-ground exercise since WWII has been about suppression or policing, not about victory. The United States has not faced a credible military threat since V Day so arguing that we "lost" iraq is facile. Saddam is gone. American firms are making money hand over fist. We have a deeply-entrenched, deeply-bloated power structure in place and it only cost us three thousand lives, countless wounded and more than a trillion dollars. That's another reason casualties are a much bigger deal: when Little Johnny died for our freedom people can take it. When Little Johnny died so KBR could get a no-bid contract to rebuild the Baghdad Museum it grates.