One of the reasons that the US Army was successful in the quelling the Phillipine insurrection is that not a single officer involved said, "We can do this the same way we did in WWII." Obviously they couldn't say that because the history had not yet happened. Many of the senior officers in the Phillipines at the turn of the century were handed down the wisdom of the Indian Wars and the pacification of the South after the Civil War.
The culture of competence in the Army at the time of the Phillipine Insurrection was shaped by a long history of localized junior officers working in concert with civilians and other government agencies to accomplish tactical tasks supporting overall strategy.
The single reason why the US Army failed in Vietnam was because the prevailing wisdom of the bulk of the US Army Officer Corps was fighting WWII set in Southeast Asia. The spectacular success of rapidly increasing the Officer Corps through Officer Candidate School during WWII was an innovation that worked in that war. Looking at the curriculum for OCS it was completely appropriate for WWII, and completely lacking in any coherent COunter INsurgency (COIN) doctrine for Vietnam.
Our greatest triumphs in WWII lead to stagnated thinking, and stagnated thinking was reinforced by Posse Comitatus, which in effect limits the policing powers of the US Military to quelling insurgency and imposing martial law.
One of the spectacular successes of Vietnam was the legitimization of Special Forces as its own branch. One of the spectacular failures of OIF is the failure of Special Forces to stop the insurgency in Iraq before it started. As the regular Army adapted to the realities on the ground Special Forces were insufficient in number to stabilize the country. In order to boost numbers Military Transition Teams (MTTs) and Police Transition Teams (PTTs) were created to provide advisers to the Iraqi military and National Police. The Regular Army developed doctrine and schools from lessons learned on the ground by junior leaders. The role of SOCOM forces have been largely focused to Ranger style raids and ambushes and intel gathering.
The ability of large organizations to change is largely a function of the mental agility of its members and the willingness of senior leaders to embrace new solutions. The difference between the officers who grew up in WWII and served in Vietnam is completely different than the officers who grew up in or post Vietnam and served in Iraq. The massive UN deployments of the Clinton Administration also shaped Army thinking to support and stability operations, just one step shy of full COIN doctrine.
Based on our current trend, our armed forces should be quite adaptable for the next 25 to 30 years. Our ability to fight a conventional war will remain high as well as the added ability to conduct irregular warfare.